gmc will shift into gear but will not move forward

What is your question?

my question is my GMC envoy. It will shift into park neutral Drive in reverse but when I shift it into drive, it will not move forward. The RPMs will just rave up. I checked underneath the driver side to see if the shifter was still intact and it was I checked the transmission oil and I also added some transmission oil. I don’t know what else to look at. Please help.