7-segment display, FND
Parts that place multiple LEDs to display numbers or hexadecimal characters are called Seven Segment Displays or FND (Flexible Numeric Displays).
It can display all numbers from 0 to 9 with only seven LEDs. So, they are widely used in elevators, rice cookers, digital wall clocks, securities companies, and vending machines.
The single-digit FND has 10 pins (legs) in each of the 5 top and bottom. There are many pins, and it may look complicated, but it's only part of the eight LED legs.
FND can be divided into cathode-common and anode-common methods according to how LEDs are tied together.
Cathodic common (left) / Anode common (right)
If the terminals on the side where the current flows are tied together, it becomes the cathode common type, and when the terminals on the side where the current flows are tied together, it becomes the anode common type.