Necessary Hardware for the RPi
The RPi comes with very little hardware.
The external components have to be found by you and then attached.
The RPi uses a Micro USB port for it's power.
You can buy these that plug into a wall, or ones that plug into a USB device (like another computer).
A lot of people have these to charge their smartphones.
The monitor that you use with the RPi can either have an HDMI plug or a RCA Plugs for composite video .
Keyboard and Mouse
You will need a keyboard and a mouse hat both connects through a USB.
The SD card is necessary to hold the OS, other software, as well and all the files that you create (like music or images).
OTHER, OPTIONAL HARDWARE...
The RPi has two USB ports.
The mouse and keyboard can use up both of these so some people like to get a USB hub so that they can plug in other components.
The RPi has a 3.5 mm audio plug.
You can use this to plug in speakers or headphones.