What's the difference between telescoped and fixed mic booms?

I need to get one or the other, and I can't go to the shop til I get paid. I can't find the info online, and I like time to think ahead. Thanks!!
if i'm not mistaken, telescoped booms can reach longer but are not as well balanced when extended all the way.
I think telescopic mic booms are the ones that can be adjusted to go up and down, longer short, etc. and fixed just stay in the same position.

I'm not 100% sure though. Hope that helps.