Transistors are used either as amplifiers or as switches.
When used as an amplifier, it can take a tiny electric current in one side, and amplify it as the electric current comes out the other side. When used this way, it can boost a current. A transistor is used this way in hearing aids.
When a transistor is used as a switch, it can store the electrical states of “on” or “off”. This equates to 1s or 0s, and is used to store binary information. This is important to know and keep in mind for other projects