What are tubes?

[ACELLR8]

I hear a lot of people talking about tubes when they mention what mods they have done to their car. What are they and what is the benefit. Are they a worth while mod for the $?

Thanks,
ACELLR8

 

[ACELLR8]

Thanks guys!
Sounds like a good mod for the $. I already have full 3" exhaust and filters so this should be a good addition.
ACELLR8