A Solo ad is simply an advertisement that is sent via email. You buy a predetermined amount of clicks from someone like me who already has an email list with subscribers that are already interested in your niche. You only pay for the people on my list that actually click over to your offer, capture page, or sales page.
I will send you targeted traffic that is already interested in what you are offering. You do nothing! I will send your offer as a dedicated email (promoting just your offer) where the entire message is ONLY about your promotion.
You get instant leads! A percentage of the people that visit your capture page will give you their name and their email (I guarantee 25% opt-ins) but you could get up to 60%! (Depending on how good your landing pages are, how good your offer is and how good your funnel is)