This is a great question and you may think it is something that computer geeks would roll their eyes at you for asking, but far from it. A Raspberry Pi is a computerintended for everyone. A Raspberry Pi is just a small computer that fits in the palm of your hand (I have large hands).
What does it have?
It has all the normal stuff you would expect for a computer like:
USB ports to plug in your keyboard, mouse, external hard drives, USB sticks etc.
Network connector to plug in your network cable
WiFi in case you do not have a network cable handy
Bluetooth in newer models
Monitor port to plug into most new TVs, monitors, home theatre systems
Sound output - so you can send sound to your speakers on your desk or to your headphones so no one else knows that you really love that annoying song
Memory and CPU - The brain stuff to make it a computer
MicroSD or SD card reader to hold operating system and your files.
Prices (and specifications) vary but you can get one starting at well under $100.
But why so cheap?
It was designed originally as an affordable way for children around the world to get their hands on a computer and learn to make software (programming). This doesn't mean it can't be used for many other things as well, like web browsing from your TV!
What do you use them for?
One of the first things I used a "Pi" for was to make my lounge room TV a computer. This was so my wife and I could see the same things on the internet without huddling around a laptop or monitor in the office.
It turned our TV into an internet browser.
Since then my kids have used them for online learning and doing their school work in the recent COVID-19 home schooling times.
Even my mum has a Raspberry Pi so when she is cold or wants to feel warm, it turns her TV into a virtual fireplace to keep her virtually warm.
Do you have more ideas?
We will follow up with more blogs about what we have done and different uses but here are some links to give you some ideas to get you started until then.