what is a solo ad and how does safe-swapsDOTcom work?

Hey guys can someone explain to me what solo ads are and how safe-swaps.com works?? i need to get some subscribers to my squeeze page !
thanks

A "Solo Ad" is an ad which is sent out to subscribers to an ezine, but without any other content. In other words, it's like a special issue of an ezine which simply contains a single ad.

Here is example of http://www.imleaks.net/solo-ads-to-10k-and-50k-im-list-becuase-the-money-is-in-the-list-guaranteed-clicks/ service.