Business Logic is a euphemism. It doesn't mean literally business logic, it means the 'core functionality of your code.' When you design software, you typically model some real world process or system in the abstract. Business logic is the core problem of your model. You can also call it model code, or core functionality. It all means the same thing - it's the important part of your app.
Using the old Asteroids arcade game [1] as an example: The business logic is how many lives the player has, what happens when you shoot asteroids (they break up, or disintegrate if they're small), what happens when you reach the edge of the map (you wrap around the other side), what kind of control scheme there is (there's momentum in asteroids, you don't stop on a dime) etc.
Using the old Asteroids arcade game [1] as an example: The business logic is how many lives the player has, what happens when you shoot asteroids (they break up, or disintegrate if they're small), what happens when you reach the edge of the map (you wrap around the other side), what kind of control scheme there is (there's momentum in asteroids, you don't stop on a dime) etc.
1) https://www.youtube.com/watch?v=WYSupJ5r2zo