Padel is typically played with two doubles teams, meaning four players total. Played on an enclosed court measuring about half the size of a tennis court, it shares the bulk of its rules of play with tennis. The main difference is that in padel tennis you can hit and play the balls off of the walls, much like in the game of squash.
Serving
With each game, you alternate who serves between the teams and the players on each team. For example: you are playing a game with Bob and you're playing against Mike and Sara. If you serve the first game, Mike (opposing team) may serve the second, Bob (your team) the third and Sara (opposing team) the fourth ... and so on and so forth.
Like tennis, your serve has to land in the diagonal box. If you are serving, for example, from the service line behind the right-hand box on your side, your serve has to land in the left-hand box on the opposite side of the net. Unlike tennis, in padel the serve is underhand.
Scoring
Scoring is also the same as in tennis. Both teams start off at 0. From there, subsquent points are 15, 30, 40 and game. If the game is tied at 40-40, you serve and your team wins the point, the score becomes Ad(vantage)-In, whereas if you serve and the opposite team wins the point, the score becomes Ad-Out. If the score is Ad-In and your team scores another point, the you win the game. If the score is Ad-In and the opposing team scores the next point, the score is once again tied. To win a game you have to win by two points.
To win a set, your team has to beat the other team by two games. A set generally has six games, unless the teams have to play more in order for one team to win by two games. A match is comprised of either 3 or 5 sets, the winner being the team that wins the majority of the sets.