NBA - Main

A very (not really) brief basketball summary:

The court is surrounded by 4 lines in a rectangle. These are the lines of play. At the beginning of each game both teams are assigned a side of the court. That side of the court is where they are allowed to score. After midpoint of each game the teams switch sides. At the center of the court is a dividing line, called the half court line. This line cannot be crossed by an offense twice in one possession. So if you bring the ball to YOUR paint, then run back to half court and cross the line, you forfeit possession of the ball. The exception being if the defense knocks the ball out of your hands and you run past half court to grab. You didn't have possession of the ball when it crossed so that would be excused.

The arc that goes around the court on both halves of a court in a U shape, that's the 3 point line. Any shot made outside of that line is a 3 pointer, obviously it gives you 3 points. Any shot made inside the line is 2 points. However at times a foul can occur. A foul occurs on certain illegal actions a defense commits. Same as penalty in football. If the foul occurs while the offensive player is shooting the ball and attempting to score, that offensive player is then awarded freethrows. A freethrow is a shot worth one point per make that has a player stand 15 feet away from the backboard and shoot wide open. Defenses are not allowed to contest freethrows. Again, if you get fouled on a shot that would give you 3 points then you shoot 3 freethrows. If the shot would give you 2, then you shoot 2. The only exception being if you get fouled AND make the shot that you were shooting. In that case, you get the points for the shot and 1 additional freethrow. Given this, the maximum point on 1 possession is 4. That would mean shooting a 3 pointer and getting fouled then making the freethrow.

There are certain situations in which freethrows are awarded on fouls that occur outside the act of shooting. For example, if a defensive player stands in the painted area directly in front of the basket for 3 seconds and has no offensive player near him then that would be a penalty. The offense is awarded 1 point for that. In addition, if the defense accrues too many fouls in 1 quarter of play then they put the opposing team into the bonus. When a team is in the bonus they are essentially awarded freethrows for EVERY foul that occurs, regardless if they were shooting it or not.

Next is goaltending. This one mostly occurs in professional leagues. A goaltend is when a defender makes illegal contact with the ball after certain thresholds. An easy way to imagine it is to picture a tall defender standing under the basket. Imagine you shoot a wide open 3 point shot and he jumps up and just puts his hand in front of the rim. Obviously this would be unfair to you because he could just stand their and do that the whole game and not actually have to guard you. Therefore any shot that is ruled goaltending is automatically counted as a make. Like I said though, that mainly occurs in professional basketball. How many regular people can really jump above the rim lol.

These are basics of the sport. What you would need to know to go to a park and at least kind of understand a game. The rest is relating to the manner in which a player can move.

As for player movement:

Any player who does NOT have the ball is free to move however they'd like in relation to themselves. Obviously you can't just sprint into other people but as far as moving your body on the court you are free to do anything.

The player who has the ball is much more limited. A player who has the ball and is still free to move is said to have a live dribble. When you have a live dribble you are free to move however you'd like and take as many steps as you like, AS LONG as the ball maintains momentum. This means as long as you keep dribbling the ball up and down. As an example, putting your hand underneath the ball for a second to make a dribble last longer would stop the balls momentum, killing the dribble. That is called a carry. Essentially you're carrying the ball and not dribbling it. Other than that a dribble STAYS live until certain conditions are met. Most notably, if you touch the ball with both hands BEFORE it touches the ground again the ball is no longer live. This does not mean you cannot move, just that you cannot dribble again unless you pass the ball and receive it back. A player who cannot dribble is allowed to take an additional 2-3 steps before they must stop moving COMPLETELY. A good example is a layup, obviously players take a few steps before laying the ball up but they are not called for travels. This is because they are using their allotted 2-3 steps.

Another key part of modern basketball is screens. This is when you see an offense player, usually a taller one, run in front of the person with the ball and stand there to block the on-ball defender. Like they're using their body as an obstacle. The person whose body is the obstacle is called the screener. This is perfectly legal in most cases. However screens can be called illegal if certain actions occur. For example, the screener MUST stay motionless while setting a screen. You are not allowed to set a screen as a screener and then just slide your feet to stay in front of the defender. If a screen is ruled illegal, the offense forfeits possession of the ball back to the defense.

To summarize: there are two and three point shots. Freethrows awarded in certain cases. A dribble can move as much as they want until the pick-up the ball. A screener can use his body as an obstacle but it must be done correctly.

I definitely missed some rulesand probably mis-explained others, but hopefully that's enough to just watch the NBA and at least keep up. As you watch more games you'll get a feel for what's allowed and what isn't. Keep in mind though, basketball is a uniquely subjective sport. You might go to a park and try a move that everyone says is a travel, then watch the NBA and see a player being allowed to do it there. Everyone has their own rules and regulations they're used to and the NBA is a bit different than what most people have played.