Boost is a feature that makes your profile visible to more users for a period of one hour.
At the end of your Boost period, you will see a pop-up telling you that your Boost is complete.
Other users will not see that you have purchased Boost or that your profile is being Boosted.
To purchase or to activate a Boost, go to your Likes You screen and tap the Boost button:
You'll know that your Boost is active when the Boost button changes to display the time remaining in your Boost:
When you receive a like that was a direct result of your Boost, you'll see a small lightning bolt next to the name of the person who liked you.
When one of those Likes becomes a Match, you'll see another small lighting bolt next to the user's name: