How to use Musical.ly, the app with 150 million users that teens are obsessed with

I remember the days of coming home from school and tuning into MTV's "TRL," a program that counted down the top music videos in front of screaming mobs of adolescent girls.

Today, teens are finding the same guilty pleasure in an app.

Musical.ly is a video network app, where users - or "musers," as they're called - create 15-second videos of themselves lip-syncing and dancing along to popular music. You can "heart" videos and create digital duets with your "BFFs," or people you follow and who follow you back.

More than 150 million people, mostly teens, have registered. If the demographic isn't abundantly clear from scrolling through the featured videos, the app also reminds you of its target user during sign-up, when it enters 2000 as the default birth year.

After talking with a handful of middle schoolers for Musical.ly tips, I entered the mysterious world of teen-tech to see what the buzz is all about. Here are the basics.