Anatomy scan/20 weeks!

Lynzee • Mommy to Ammarie, born on March 3,2016!
So, what should I expect from this appointment? I know they're going to do a detailed ultrasound, but what else? 
Also, my husband wasn't able to get out of work to go to this appointment, so his mom offered to come in his place so I wouldn't be alone. Would this be an appropriate appointment for her to go to?