It's primarily a skill game, although luck plays a huge role. In any single given hand, luck is the predominant factor in who will win or lose. However, poker players don't play a single hand. They play hand after hand after hand & and overall, skill dominates.
Poker has a gambling element to it, which leads some players to question if poker is just down to luck. Although there is a serious amount of luck involved in poker, the fact the same big names regularly win in cash games and tournaments shows that there is skill involved.