vaginal ultrasound

Have you had a vaginal ultrasound? My first appointment is next week and I've heard about a lot of people having them. I didn't even know what it was until I looked into it. If you've had one can you tell me what it's like? Comfort level? Anything like having a pap? Or is it less or more uncomfortable than that? I saw the "tool" and it seems pretty big in every way. Hoping I'll just have an abdominal one, but just in case I'd like to know what I'm in for.  Thanks!!