My tooth is suddenly crooked after 1 year of braces and haven't gotten my braces tightened in 3 months. does that affect anything?? do teeth move??

Quite Possible: It's unlikely that just one tooth would move randomly while you're receiving orthodontic care. I assume you're wearing regular metal braces? If that's the case and just one tooth has moved, it's possible that a bracket has come loose, or something else has gone wrong. Three months is a long time to not see your dentist/orthodontist during active treatment. Sounds like you should get checked asap.

Yes they do move: Since you have your braces on get back to dentist and he can evaluate to get that tooth aligned. Now keep all of your appts very important

Orthodontics: If there is a stable bite, teeth tend to move minimally if at all. However, when you have Orthodontic treatment, there is a tendency for the teeth to go back into their original position, especially in the first year after Orthodontic treatment is completed. That's why it is essential to see your Orthodontist for all scheduled appointments. Also why you need to wear a retainer, sometimes for life.

Absolutely: It's not like taking a steel post and putting it into concrete. Bone is a living changing tissue. Orihodotontic treatment is an ongoing process that requires supervision. If you have not seen your treating Dentist or (hopefully) specialist Orthodontist, what you perceive as untoward movement of one tooth may just be the tip of the iceberg. See your provider ASAP.

That's the idea: Orthodontics involves moving teeth--if one appears out of line, that's exactly why you have the braces in the first place. Speak with your orthodontist and she/he will have an answer for you right away :)