Add-on (noun)

1. A software or hardware component added to a computer or program to give extra features or functions.
2. A supplement or accessory added to something else.

Origin:

Mid-20th century: from add + on.

Examples:

1. A browser add-on that blocks ads.
2. The game came with several add-ons that expanded its gameplay.
3. A new add-on for the flight simulator program.
4. The add-on to the car allows it to run on electric power.
5. An add-on feature to the phone's camera.