What are the weapon skins in CS:GO and how to get them?

Weapon skins in CS:GO are various visual weapon modifications that can be obtained in-game or purchased on the Steam trading platform. There are several ways to get weapon skins:

End-of-round drop-off: players can get skins when they win at the end of a round.
Opening cases: players can buy keys to open cases with random weapon skins.
Buying on the Marketplace: players can buy or sell skins on the Steam Marketplace. The price of skins depends on their rarity and popularity.