FIFA coins are in-game currency in EA Sports FIFA game with which you can buy in-game items and packs in FIFA Ultimate Team game mode.
Using FIFA coins, you can get packs from the store, items and players on the Transfer Market, or enter the FUT Draft mode. FIFA coins can be earned by playing matches, completing objectives or trading items and players on the FUT Transfer Market.
Coins are stored in your personal FIFA account and there is no limit to earn and store coins in your account. Unlike FIFA points, your FIFA coins will not be carried over to the next version of the game. So, to make the best out of your coins, you should spend your coins for buying and items before you're moving to the new of FIFA game.
Keep this in mind that buying or selling FIFA coins is against EA's Terms of Service; in other words, buying and selling FIFA coins is unlawful, and doing so will result in your account being permanently banned by EA Sports.
If you are planning any transaction regarding this matter outside the game, make sure you are familiar with the rules especially before you buy FIFA 22 coins or sell your coins on the third party websites.
According to FIFPlay website, in real money, a FIFA coin does not have a defined worth. However, one FIFA coin is roughly assessed at USD 0.0002 if you want to measure the work required to obtain FIFA coins by playing FUT matches. In other words, $1 is about equal to 5,000 FIFA coins.
The best way to earn FIFA coins in FUT 22 is to play matches, complete objectives, solve SBC challenges, and trade players on the market.