If you have crowded teeth willthat mean you need braces?

Not self correcting. Crooked teeth are harder to clean, tend to wear unevenly, strain the bone/gums that support the teeth, are "lost" more frequently than well positioned teeth, and are unsightly. Why not consult with a qualified orthodontic specialist who can evaluate your malocclusion and talk to you about treatment options. Go find out.
Options.... If your crowded teeth bother you, are hard to clean, or both, then you might want to consider braces. How long do you want to keep your teeth? This question seems trite, but is really why you should consider treatment. Well aligned teeth are easy to clean, don't chew themselves to pieces and will last a lifetime with proper oral hygiene.
Braces. Crowded teeth are harder to keep clean and may not occlude/come together the way nature intended causing excessive wear. Braces are a great because they can make the teeth easier to keep clean and healthy. Braces can realign the teeth so they function for a lifetime they way nature intended.
Yes! ideally. If your teeth are crowded they are more difficult o keep clean, and as they are naturally drawn forward they will become more out of alignment. Haven't you seen the little lady at the wedding complimenting you and noticed her crooked teeth. They weren't always that bad, they progressively got that way. So if you want attractive teeth straighten them before they get worse.