Ping: Time taken to send a signal from your computer to another server. (Measured in milliseconds)
Download: Time taken to download something from another server (Measured in Mbps (Megabits per second, NOT MEGABYTES) 8 Megabits = 1 Megabyte. Download speed is good for downloading games/files and watching online videos)
Upload: The reverse of download; Time taken to send something to another server (Once again, measured in Megabits. Upload speed is good for Uploading/Sending pictures and streaming onto Twitch)
Btw, if you get 800 Mbps Download, (Which = 100 MBps), it will take approx. 1 second to download a 100 MB file.
Mb = Megabit
MB = Megabyte