Each folder will also contain resource and behavior pack folders to contain any packs that may be in use within the world. MinecraftWorlds contains each world that has been generated within the current build of Minecraft. Development pack folders are updated each time Minecraft is launched so you can quickly load and test the changes you made to their contents. The development_skin_packs folder is used for developing skin packs. You will use the development_resource_packs and development_behavior_packs folders for the Resource Pack and Behavior Pack tutorials.
Don't worry about these folders right now - you are going to be developing content, so you will be working in the development versions of these folders, as discussed in the next section.
There are three folders called behavior_packs, resource_packs, and skin_packs that will store finalized custom content that will be added to Minecraft: Bedrock Edition. If you see more content in this folder than what is shown above, do not panic! This image shows a fresh install of Minecraft.