I'm assuming the OP doesn't know what you just said since she said she has no idea what auto focus and manual focus is.. so if that's the case I'll tag onto what William said (which was great advice by the way!)
CatsRants, 1. when getting your camera find out if it has Auto focus in video mode (meaning it will focus on you automatically). If not then you'll have to manually focus your lens when filming. Most lenses now have an AF/MF switch (auto focus/manual focus) so if your camera has auto focus on video mode you can leave your lens on AF, but if it doesn't then you'll need to move the switch to MF when filming.
2. Do some quick research on how aperture works. The 50mm f/1.8 just mentioned means the maximum aperture is 1.8. It mainly deals with how much of your shots will be in focus and how much light can be let into the lens. That was a super quick explanation but it's interesting stuff to read up on
3. Speaking of 50mm also read up on how focal length works. The "millimeter" in 50mm refers to the focal length and it will determine how close your subject appears to be to the lens. Also very interesting stuff and good to know if you're an aspiring vlogger or filmer or photographer etc. It's kind of like a "zoom" but not quite the same.
Once you read up on those you'll have a much better understanding on what lenses to invest in in the future. Then what I always do (and most people do too) is read plenty of reviews on lenses before buying. Then start saving up some money so you can get them and start having some real fun!