A small explanation first about solo ads and how they are delivered to their target audience:
It really depends on the provider! Generally these people own blogs, websites, instagram accounts, facebook groups etc, through which they collect emails to build their email list in different niches.
Then, depending on their niche, they can promote your product (Presell page or direct hoplink) to their email list, and therefore make people click on it. If you don’t have an ad text, then it’s the seller’s responsibility to choose their own way to promote your link, and they can do it any way they choose. (Whether it’s good or not is questionable, again, since you DON’T KNOW what they do, that’s why John provides the texts, and you should always add your own ad text if available)
The targeted audience is not very “warm”, since, even though they ARE interested in the niche that you are promoting, they are not necessary interested in buying your product, unlike the clicks you get from google & Facebook, which you can target better and you know at least partially WHO is clicking your ads.
The advantage is that you know exactly how much a click will cost and how many (at minimum) clicks you are going to get.
So let’s say I own a blog about traveling and I publish twice a week, through the years I collected an email list of 10,000 people which are my blog readers and newsletter subscribers. I now offer my services on Udimi. You buy from me, 100 click for your product, which is an extra light sleeping bag . I know by experience that to get 100 clicks, I need to send your product to about 1000 people. So I send them your email swipe ("Hey guys, everybody is using this new awesome sleeping bag now, check it out here! "), and I got you 132 clicks for example (over delivered).
I always advice customers to wait a little for module 2, to get their website/presell page up and running, before investing in Solo Ads, or throw up a little budget on it to try it out, ‘test the waters’