Hello Chuh00, "x" means kiss "o" means hug "xo" kisses and hugs "xoxo" kisses and hugs, kisses and hugs ;) It is used informally ( never in formal letters or emails ,usually at the bottom of the letter ) between friends or acquaintances not necessarily close friends.

Cherry is correct, only use xoxo with close friends or family. It's the same with swalk[ sealed with a loving kiss]