2 questions: CV boot vs. Power steering boot?? and sound?

Hi,

My mechanic said that I'm missing power steering boots on my car. But when I search, i'm finding listings for two things: cv boot and power steering boot. What are they, what do they do and how do i put them on?

Also, my car makes a thumping or thudding sound when I drive. I thought it was just the tire (which i changed because it had a bulge in it). HOwever, the sound is still there, after the tire change (though it is a lot lower in amplitude). What could be causeing this? Is there anything that causes tires to get bulges?

Thanks