Video games are one of the better examples of OOP because it is fairly literal. Many objects are things that you can actually place, move, and interact with.
At a fundamental level though, they are just contained bundles of data and code. Some are pure data, which are often used as messages. Some are pure code, which are often used as helper classes. Some are data and functions that make sense. Making a demo game in Unreal Engine 4 is a good idea, such as Minesweeper or Breakout, although I am obviously biased to that. For the most part, it will just cement the first four sentences of this paragraph, though.