Itunes is asking me to 'Download all' my old songs? Itunes expert needed please!?

A while back I had hundreds of songs I bought on Itunes and then my computer crashed so all my songs were lost and now im looking and when you go in the Itunes store tab then click on the right hand side that says Purchased (NEW) and when go into that it has all my dnogs that I once had but now dont and at the bottom it says Download all. So if I click on it, will it give me my songs back? If so, will it charge me again for the songs????