An autodialer is a machine that calls thousands of numbers an hour.
Usually we'll get a call from our doctor's office from an autodialer to remind us of an appointment, which helps us out..
The TCPA protects us from calls that are made to us without our permission. Such as from telemarketers or debt collectors.
One of the requirements for the TCPA to apply is that an autodialer must have been used to call you.
Hope this is helpful.
Have a great day!