I've kind of looked at them, which confused me and how you can use them. Please explain the usage of them if you could. Roblx APIs
I am glad you asked this! First off, I recommend you use this instead, as it is on the site, and probably more reputable. https://developer.roblox.com/articles/Web-APIs
As for how to use them, you can't use them inside a Roblox game. This is because their HTTPS service will not allow us to use anything that links to the site in a game server. However, many developers have worked around this. It's a simple work around, if you're willing to learn another programming language. I personally prefer JavaScript to solve it. What you end up doing is making a JavaScript webserver. From there, you send http requests to this webserver, which will send requests to those api links and return the responses to you on a roblox server. It's not the most efficient, but it's what we've got. If you choose to specifically learn NodeJs, which is very useful for this, you can install some modules. I can use XMLHTTPREQUEST, which is what is built into most browsers now. Alternatively, you can use another module called http. That's simple to use, and doesn't require you to make an async function to use it.
An example on how I use it on my webserver is:
https.get("https://www.roblox.com/Game/LuaWebService/HandleSocialRequest.ashx?method=GetGroupRank&playerid=" + JSON.parse(RoVerResponse.toString()).Id + "&groupid=72321", (res) => { res.on('data', (RobloxRankResponse) => {
Keep in mind, you'll have to learn another language, or figure out how to make a webserver in lua and host it.