A Raspberry Pi is a minicomputer. The minicomputer is about the size of a credit card and fits easily in your pocket. It is a circuit board and contains all the important components a computer needs, such as the ARM processor and all the necessary connections.
Suppose you were to connect a monitor, mouse and a keyboard to the Raspberry Pi, then you just have a real computer. As we just mentioned, the Raspberry Pi contains many connections that a “regular” computer also has, such as USB, UTP port (Internet port), HDMI and micro USB (Charging port/power supply).
The Raspberry Pi has no storage and therefore you do need a micro-SD card, otherwise you can’t do much with it. You can easily insert the micro-SD card into the micro-SD slot/slot.
On this micro-SD card you put, for example, software that you have programmed yourself. With this you control for example motors or process data from sensors. It is also possible to put an operating system on it, which is easier to work with when connected to a monitor.