You've probably seen the ads.

You're scrolling through Facebook, and - bam - a 17-year-old teen with blue contacts, bleached hair, and fake blood dripping down their neck appears in your news feed, lip-syncing to some catchy tune. What is this, you ask? It's TikTok. And it's about time you checked out the app.

What is TikTok?

TikTok is a social media app. As of September 2018, it surpassed Facebook, Instagram, YouTube, and Snapchat in monthly installs in the US Apple App Store and Google Play Store. And it has over 500 million global monthly active users. Its Chinese parent company, ByteDance, is considered the world’s most valuable startup, with a valuation of more than $75 billion. It's so popular that Facebook even launched a competitor.

If TikTok sounds familiar, it's because you probably recall similar apps that came before it, like Vine and Dubsmash. Also, its predecessor is a service called Musical.ly, launched in 2014 by Chinese entrepreneurs Alex Zhu and Luyu Yang. That app was acquired by ByteDance in 2017, which folded Musical.ly into its own TikTok app last August. Existing Musical.ly users were automatically migrated over to TikTok accounts.

Users basically woke up one day and saw that the Musical.ly app on their phone had a new brand and interface, but the same core features.

How does TikTok work?

Getting started

The basic function of TikTok is that users can film videos of themselves lip-syncing or acting out sketches. Their videos can be up to 15 seconds long. They can pick from a library of songs, effects, and sound bites to add to their videos. They can also “duet” with someone by replying to a video, creating a split-screen and endless reactions. Users can even add their own sounds and lip-sync to another user's original video.

Navigating the app

In a nutshell, like videos from Vine or Instagram, TikTok videos are vertical. You can engage with “hearts", which are the same as “likes.” After you download the TikTok app and open it, you'll immediately see curated featured videos, labeled “for you". You can switch to “following” to see videos from the people you follow - whether they're friends, or popular “Musers". Click the home button in the bottom left for more new videos.

You can also try the magnifying glass icon next to the home icon to search keywords and hashtags. Within videos, tap on the screen to pause, or look to the right side for the user icon to go to a user’s profile or see the number of “hearts” a video got and the number of comments.

On the bottom of the video, you'll find the user’s name, caption, and the name of the song that’s playing. Click on any song to see related videos.

It’s possible to watch videos without creating an account.

Posting a video

When you’re ready to post your own video, click on the plus sign at the bottom of the home screen.

To make a TikTok video, you should sing and dance to music, or perform a sketch. While that sounds easy, it takes a tonne of work. If you search YouTube for tutorials, you'll see how intensive the TikTok video-making process can be for most users. We've provided an example above. If you're looking for step-by-step instruction on how to use the app, we recommend trying TikTok's Support hub.

Who to follow on TikTok

Oddly, celebrities and popular influencers on other platforms haven't been quick to adopt TikTok. But we've seen Jimmy Fallon's team publish weekly games like the #TumbleweedChallenge, and Amy Schumer recently uploaded her first TikTok. Tony Hawk, too, is a TikTok user

Some OG TikTok users have also become stars in their own right. For instance, 16-year-old twins Lisa and Lena have 32 million fans, while 18-year-old Baby Ariel has 29 million fans, and 16-year-old Loren Gray has 29 million fans. Each of them have gone on to release their own singles.

We recommend scrolling through TikTok to find users who you personally enjoy. But be warned: A lot of it is corny. You'll see numerous American teens essentially doing Karaoke while trying their hardest to look provocative or cool on camera. Sometimes it is cringey, other times it is painfully awkward or feels wrong to watch. But many of these videos have even gone viral and become memes. 

There's the finger dancing meme, and the challenges where you lip-sync to Ice Age or rotate your phone, for instance.

Should you try TikTok?

It can't hurt to download the app and see what it's about, though we suspect it'll make you feel old, instantly. Users on the app tend to be young, in our experience. In fact, there are so many high school-aged users that, when you see an adult pop up in the featured video feed, you can't help but feel like they're out of place. Maybe that'll change one day, especially as more celebrities embrace the service. 

According to Digiday, 50 per cent of those who use the TikTok (Musical.ly) app on iOS were between the ages of 13 and 24. On Android, it's 60 per cent. Female users also outnumber males on both platforms. Like any social network, there are reports about adults using the app to inappropriately contact kids. While there are privacy settings available, there are no parental controls