What do US sanctions on Russian oil mean, and who could be affected?

The US has imposed sanctions on Russia's top oil companies, Rosneft and Lukoil, to pressure Moscow into ending its war on Ukraine. These sanctions could impact Russia's economy significantly, as oil and gas account for about a quarter of its federal budget. Additionally, the sanctions could affect global oil prices, causing a 5% rise in Brent crude following the announcement. Countries like China and India, major buyers of Russian oil, may also be impacted as the US urges them to stop purchasing Russian oil and find alternative suppliers.