Adaptors do one of two things. Adaptors can match the electrical requirements of two devices. And also, adaptors can match the physical characteristics of one tool or device to another. In some cases, adaptors do both.
We use adaptors in many of our things. One common type of adaptor is used for plugs. Sometimes we have electronics with plugs that won't fit into an electric socket because of differing pin configurations. Adaptors attach to the power plug of electronics so that they may be plugged into the electric wall socket.
More complex adaptors actually change the voltage from the wall socket into a higher or lower voltage, depending on what is needed by the electronic device. Such adaptors have transformers in them which can, for example, convert 100v to 240v, or vice versa.
Other adaptors allow us to use devices on gadgets that normally wouldn't accept them. For example, adaptors can be purchased to allow a particular video tape format to play on a video camera or player that uses a different format. Adaptors also allow the use of input devices on systems that don't use those input devices. For example, with the use of adaptors, you can connect video game console controllers to a PC.
Adaptors may also be as simple as something used to attach two garden hoses together. If a garden hose's reach is not long enough, two garden hoses can be attached. However, one end of a garden hose normally will not attach to another. In order to connect them, special adaptors need to be used.