Sorry if the question makes no sense, yeah what is it and why is it important. Ive tried googling it but the info just goes straight over my head. I have nfi what they are talking about.

The reason im asking is i was going to buy an amp off someone and they kept asking me if my box is tuned and if the frequency is blah blah blah and im like dude i just need an amp!

Thats makes no difference to the amp!
Just buy it if you like it!

Cheers
Pete

P.S. I just wrote a whole post on resonant frequency and then re-read your original post and it had nothing to do with it LOL

It doesn't really have anthing to do with you buying that amp. Resonant freq is between your sub, sub enclosure and your vehicle. Google for answers :P If I was to try and explain it again, you'd probably have the same reaction