Hand ranking is essential to poker and since most games revolve around the best 5 card hand that is what I will provide rankings for. Hands start at the bottom left and and move left then up, one pair, two pair, three of a kind, straight,etc. If there is no ranking hand then high card decides winner, for example a hand of A9652 vs. a hand of A9675, the later will win. both hands do not rank and both have the same top card however the forth ranking card in the second hand is a 7 making that the winning hand. the hands are ranked as such by their rarity, a straight will happen more often than a flush, the difference in frequency will depend on the game. I will get into probability when I discuss strategy, this is still intro level: assuming you know nothing.
Note: wild cards (req. for a 5 of a kind) will usually only appear in a 5 card draw game however many games vary from location to location. House rules always apply.