Hi,
Look no further than the Cow for tutorials on AE:
https://www.creativecow.net/show.php?page=/articles/aftereffects_basics.html
https://www.creativecow.net/articles/aftereffects.html
You can certainly find more tutorials out on the web, but it’s such a deep program that I’d generally recommend you find a good book or training series. My favorite books are “Creating Motion Graphics with After Effect” by Chris and Trish Meyer. The Total Training video series is excellent. There are cheaper options out there, though.
AE can be used for, well, a lot. Do a search for “after effects demo reel” and you’ll find a lot of hits. Adobe has some examples of what people are doing with AE on their site:
https://www.adobe.com/motion/customerstories.html
You might also want to visit the web sites of some of the leaders at the CreativeCow AE forum and look at their reels:
https://forums.creativecow.net/cgi-bin/new_view_posts.cgi?forumid=2
Aharon (allbetsareoff.com) and Andrew (videocopilot.net) in particular have some nice sites. Keep in mind that most artists use more than one tool, so you’ll see a lot of 3D modeling mixed with compositing and effects work in AE.
I couldn’t tell you if AE really is a standard in the video industry or not. All I can say is I know that a LOT of people use it. Different people prefer different programs, and your friend obviously has his preference. AE is not the end-all be-all of motion graphics and compositing tools. AE does some things better than other programs, and other programs do some things better than AE. But no matter what program you choose to learn, you’ll learn a lot about the craft, and that’s what is important, not what particular tool you use.
One more thing- there is an amazing number of plug-ins available that extend AE’s capabilities. After you get used to the basics, try downloading some of the demos, like the Trapcode plug-ins, and see what kind of amazing things you can do with them.
AE is a complex program, but so very very cool. There’s a lot to learn. Enjoy it.