Could be a bearing, ball joint, or bad axle (if your car is front wheel drive, you should post the make, model and mileage). It could also be a bad control arm. All could be dangerous and need to be fixed. Most of these repairs run in the $100-$500 range. Find a good shop and get an estimate. If it seems high, take it to another shop and see what they say.

Could be anything, take it to a couple shops and ask to have the front end checked.

Could be a suspension bush or bolt loose. Exhaust knocking on body work etc.

not a tie rod end. loose bolt or bad bushing.

front wheel drive? check cv joints?

I'm not sure if what I have is related to the tie rod at all, but someone I know said it might be. When I'm turning and/or breaking (honestly, I don't know which it is, given that I usually do them both at the same time... but I'm pretty sure it's turning), I hear a really hard click noise and I feel it kind of right under my feet. The only thing I can think of that it sounds like is when the gas pump stops itself.

If that's not my problem, what is it? How much could it cost to fix, whatever it is?