Slip

I was driving my car when I got of work and went to do some stuff before going then I went home to grab something I left the car running in the driveway it was working perfect before going home and as soon as I got of the drive way I notice the transmission was acting weird. The rpm's were increasing but speed was not. So I turned down a side street and put the car in park and turned it off and restarted it. Put it back a drive and it then it was working again. Once I got to the stop sign and came to a complete stop it did it again. It would not go so I turned it off and restarted it then it worked. So I took it to Auto zone because also the check engine light was on. They put it on the computer and the speed sensor popped up and so did transmission reverse first. But do not know what that is. Can someone please help me so I know what I am dealing with? Thanks