When you create a 2D video game, much of your levels or worlds will have repeating elements. It would take too much world to draw huge levels.
The way to avoid this problem is by creating tile maps, small blocks that can create larger environments. Think of it like Minecraft but in 2D.
Creating a Tile Map
Tilemapping is all about layers. Create your bottom layer such as grass on layer 1. Layer 2 would be trees. If you try to put them on the same layer it cuts a hole out.
Here are some great examples of tilesets:
Here’s an example of some of my creations: