These little jobs are done by people who log on to a company’s site and choose tasks, which could be as simple as clicking a link. Amazon's Mechanical Turk is one of the most well-known sites of this type. Also, there are crowdsourcing projects, which are similar to data entry, where companies engage an army of virtual workers to each do one small part of a larger project.
A word of caution: Remember that where very little is required, very little is offered. These jobs don’t pay much, and they are not going to provide a reference for your resume. It may take working at several different of these online jobs to pull in the income you want. And as always, know the signs of a work-at-home scam as you sort through the opportunities.