Both blinds and an ante are forced bets. Both are made before the cards are dealt. However, if blinds are made by only two players (who sit left to the dealer), ante is something all players have to do. It is better to view ante as a sort of payment for participation in the game and something that constitutes the pot. Ante is a relatively small “payment”, usually one-tenth the size of the big blind.
The main purpose of the ante is to prevent the artificial prolonging of the game – the players who otherwise would have constantly discarded their hands in the search for the better one are now forced to actively engage in the betting, or they lose their chips.
Antes are not always present – you better carefully read the description of the table before playing. “Casual” games are not guaranteed to have an ante, and games featuring blinds often lack it. However, its presence greatly affects the game – even in the preflop stage, a significant pot is already available, which speeds up the game and makes it more engaging. This is why ante is often seen in tournaments, especially in the later stages. With ante present, more players remain in-game with their cards in hand, rather than folding, which makes for good ratings for televised tournaments. Most televised high-stakes cash games also use both blinds and antes.
In live cash games where the acting dealer changes each turn, it is possible that the dealer pays an ante for each player.