They were already supposed to be illegal in Indiana, but telemarketing robocalls are banned on the federal level starting Tuesday.
Basically, a robocall involves an automatic phone dialer and an automated message. You’d get a robotic-sounding voice (hence the name) telling you, for example, that the warranty on your car was about to run out, and to press “1” to extend it. The implication was that the call came from the automaker itself, only it didn’t. Quite a few people have been suckered out of a few thousand dollars each because of these things.
There are some exceptions to this new rule, of course. You should still sign up for the national Do Not Call Registry, as well.