There are no sanctions imposed by the United Nations against Russia. (Russia is one of the five permanent members of the UN Security Council so any effort to impose sanctions will be vetoed by Russia.)
The EU sanctions against Russia and Ukraine is based on four segments:
COUNCIL Regulation 2014/386/CFSP of 23 June 2014 concerning restrictive measures in response to the illegal annexation of Crimea and Sevastopol (Broad trade and financial sanctions regarding Crimea and Sevastopol regions)
COUNCIL Regulation 2014/145/CFSP of 17 March 2014 concerning restrictive measures in respect of actions undermining or threatening the territorial integrity, sovereignty and independence of Ukraine (Travel ban and Asset freezing sanctions for threatening the territorial integrity, sovereignty and independence of Ukraine)
COUNCIL Regulation 2014/119/CFSP of 5 March 2014 concerning restrictive measures directed against certain persons, entities and bodies in view of the situation in Ukraine (Asset freezing sanctions for Misappropriation of Ukrainian State funds and persons responsible for human rights violations in Ukraine)
Council Regulation (EU) No 833/2014 of 31 July 2014 concerning restrictive measures in view of Russia's actions destabilising the situation in Ukraine (Russia sectoral sanctions)
This regime is a mix of comprehensive and list-based sanctions. It is mainly consisted of the following measures:
Following a series of events that took place in Crimea peninsula in February and March of 2014, the United States President declared a national emergency on March 4th, 2014, by issuing E.O. 13660. This executive order marked the beginning of a complex program against Russia and Crimea region. This executive order put in place a number of grounds for designation of persons and imposed travel bans.
Few days later, on March 16, 2014, the President expanded the designation grounds by issuing E.O 13661. This executive order, among other things, provided the authority for designation of officials of the Government of the Russian Federation. Few days later on March 20, 2014, President Obama issued E.O. 13662 and targeted certain sectors of the Russian economy. This E.O. is the basis for the United States sectoral sanctions. Even though the language of the executive order suggest the sanctions pursuant to this order should have been blocking sanctions, section 1 (b) of the order provides for limitation of the scope of sanctions through different instruments namely directives. Accordingly, on July 16, 2014 following the determination made by the Secretary of Treasury, OFAC issued Directives 1 and 2 (first version) targeting financial and energy sector of the Russian economy. The restrictions imposed by the Directives were not blocking sanctions, rather they prohibited transacting in, providing financing for, or otherwise dealing in new debt of longer than 90 days maturity or new equity for these persons, their property, or their interests in property. On September 12 of the same year, the Secretary of Treasury issued amended Directive1 (second version), amended Directive 2 (second version), Directive 3 (first and the only version), and Directive 4 (first version). The amended and new directives put in place new restrictions which are all detailed below. OFAC again amended the Directive 1 (third version) and Directive 2 (third version) to decrease the permissible periods for debts. OFAC finally amended Directive 4 (second version) on October 31, 2017 and expanded the scope of previous Directive 4. You can see the restrictions imposed by each of these Directive in different stages below.
Directive 1 targeting financial sector of Russia's timeline
Directive 2 targeting energy sector of Russia's timeline
Directive 3 targeting defense sector of Russia's timeline
Directive 4 targeting energy sector of Russia's timeline
In December 19, 2014, President issued another executive order with respect to the situation in Crimea (E.O. 13685). This executive order marked a major expansion of the sanctions against Russia by imposing a comprehensive set of sanctions agains the Crimea region of Russia. The executive order also provided additional grounds for designations to the SDN list.
Another major milestone in Russia sanctions program was passage of CAATSA. President Trump after a long delay on September 20, 2018, issued E.O. 13849 to implement various sanctions required by the Congress. CAATSA required the executive branch to produce several reports. It also required the President to impose certain sanctions with respect to Russia. It also provided the options of adoption some other sanctions against Russia. Among theres mandator and optional sanctions are sanctions with respect to activities of the Russian Federation undermining cybersecurity, sanctions relating to special Russian crude oil projects, mandatory imposition of sanctions with respect to significant corruption in the Russian Federation, mandatory imposition of sanctions with respect to certain transactions with foreign sanctions evaders and serious human rights abusers in the Russian Federation, sanctions with respect to persons engaging in transactions with the intelligence or defense sectors of the Government of the Russian Federation, sanctions with respect to the development of pipelines in the Russian Federation, sanctions with respect to investment in or facilitation of privatization of state-owned assets by the Russian Federation. Some of these sanctions were implemented and had major effects. For example designation of several Russian oligarchs in April 2018, sanctioning an entity for its role in NordStream II project in January 2021, and sanctions against Turkish entities for acquiring S-400 defense system from Russia.
Finally, section 230 of CAATSA made it difficult for the President to lift certain sanctions imposed against Russia by requiring the President to take certain steps before such terminations.
Another round of sanctions agains Russia came after the the attack with a chemical agent in attempt to assassinate the Skripals in Salisbury. The United States Department of States and Treasury took some actions as result of this attack. As far as it related to the Department of Treasury, OFAC issued the CBW Act Directive in line with E.O. 13883. This Directive prohibited U.S. banks from participating in the primary market for non-ruble denominated bonds issued by the Russian sovereign and also prohibits U.S. banks from lending non-ruble denominated funds to the Russian sovereign. For further information about this program you can check Chemical Weapons Sanctions dedicated page.
Sanctions agains Russia are very complex and subject to several changes. As of early January of 2021 there are several bill in Congress which if passed would require additional sanctions.