What is Captcha Entry - is it entering the captcha for non-human programs?

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I saw another mylot discussion talking about making money with captcha entry. It didn't sound like it paid a lot, but then most online work only pays with volume. However, I am not sure what they are doing when they say it is captcha entry. Surely, they have programs that make up the random captchas? Are you entering captchas for computer programs? Is it typing in the captchas to allow computer programs access to things? The whole idea worries me a bit, since captchas are used to keep out bots and spam and if humans are employed to enter the captchas for them, they are just helping to fill the internet with spam. I wouldn't be interested in this kind of work.