I want to know how to use it, as it is a pretty neat function, and I may have use for it.
HttpService is used to send HTTP GET/POST requests, using HttpService:GetAsync() and HttpService:PostAsync, respectively.
To use it, run the following in the command line:
game:GetService("HttpService").HttpEnabled = true
This will allow you to use HttpService in your game when it is online.
HTTP GET fetches the html content of the given webpage.
HTTP POST can be used to send data from your game to a website to be processed, such as saving it in a database.
If you need to use it, you will need to setup a website.