Slavic Languages
The Slavic languages are a branch of the Balto-Slavic languages, which themselves belong to the Indo-European languages. They are spoken mainly in Eastern Europe. Russian is the most relevant Slavic language in the world, being one of the ten most spoken languages in the world, since it's spoken in Russia as a native language and in the other post-Soviet states as a lingua franca. Other important Slavic languages are Polish, Serbian, Croatian and Bulgarian.
Subgroups
The Slavic languages are divided into 3 main subgroups: Western (Polish, Czech, Slovak...), Eastern (Russian, Ukrainian, Belarusian...) and Southern (Bulgarian, Serbian, Croatian...). Languages of each subgroup are more related to each other than to the languages of the other subgroups. The Slavic languages of each group are very similar to each other.
Russian
Russian is a Slavic language that belongs to the Indo-European language family. It is the official language of Russia, Belarus, Kyrgyzstan, and Kazakhstan, and is spoken by over 258 million people worldwide. The language uses the Cyrillic script and has six cases for nouns and adjectives, which can make it challenging to learn for non-native speakers. Russian literature, art, music, and cinema have made a significant impact on the world, with famous authors like Leo Tolstoy and Fyodor Dostoevsky and composers like Tchaikovsky and Rachmaninoff. Russian is also an important language for international diplomacy, given Russia's status as a major world power.