A sports betting tout is an individual (handicapper) who sells picks often in exchange for an up-front payment. Touts either sell picks by themselves or are part of a service, which is composed of numerous touts, selling different kinds of packages.
The most common way touts make money is by selling a package of picks for a certain amount of time, often a full season or over the course of the playoffs or a tournament. Each tout works differently in that they'll charge a one-time fee for a set of picks or they'll charge on a per-pick basis. From there, some touts also charge a winning percentage, which is a tad more fishy, as you'll have to pay the original fee and another fee for a percentage of your winnings.
While touts often promote huge winning percentages and guaranteed winners, most of them can't be trusted. The theory is that if you are a successful bettor, you don't have to sell your picks. That's why touts get a bad rap because in addition to hard-to-trust betting numbers, it's hard to verify the thousands of picks they say they've made in the past. Even then, some of them will give out different picks to different subscribers for the same contest.
Even if the tout gives out winners, it probably isn't worth it in the end unless you're a high-stakes gambler. Sports betting is already difficult in order to come out on the positive and hit roughly 52.4% of bets. Throw in the extra few dollars spent on a tout service and that percentage can rise to 55 or even higher, assuming you want to win something. If a tout advertises to give winners at more than a 70% clip, that's when you run. Hitting more than a 60% clip is a rarity and if that's the case, that bettor should be rich.
If you want to be a successful sports bettor, it's going to take more time than finding a random tout online and giving them money. Most successful sports bettors have a system of numbers they use in order to take bias out of the equation. You can find almost any piece of information you need for free online and that's usually the best place to start if you're serious about sports betting.