The dealer is the one who gives out the cards.
He doesn't actually have to be dealing the cards, but he is the one who would do it according to the rules, and the order of action therefore progresses as if he were dealing.
In Texas Hold'em, each player therefore takes a turn being dealer, even if the one actually giving out the cards is a casino employee or software program. The dealer designation moves clockwise around the table from round to round, even though the actual dealing is not performed by the players. At every stage the current dealer is denoted by a small chip, called the dealer button, which also moves around the table in clockwise fashion.