Seven LEDs arranged in a rectangular fashion as shown. Each of the seven LEDs is called a segment.
There are two types of LED 7-segment display called Common Cathode (CC) and Common Anode (CA).
The Common Cathode (CC) – In the common cathode display, all the cathode connections of the LED segments are joined together to logic “0” or ground. The individual segments are illuminated by application of a “HIGH”, or logic “1” signal via a current limiting resistor to forward bias the individual Anode terminals (a-g).