When it comes to beach volleyball court positions, it's pretty simple. There's only two players on the court on each side. You have your left-sided player and your right-sided player. You and your partner can switch sides at any time if you'd like, but most people tend to be either a right-sided player or a left-sided player.
When you're playing defense, typically you have a blocker. That's the person that's up at the net, ready to press their hands over the net. Then, the person behind them, filling in the space that they're not covering, that's the defender. Sometimes you have both people playing defense. That's called two-down defense, and both people are kind of in the servicing position, left and right side. You adjust around on the court depending on where your partner is. It's almost as if there's a string between you. You don't want to get too far away from your partner, or you don't want to crowd them; you want to be just close enough to control the ball.
And that's how you position yourself on the court for beach volleyball.