Behaviour packs, also known as Addons, are the closest thing Bedrock has to mods. They allow you to adjust many of the vanilla behaviours of the game as well as adding new things to it with. Experimental features are ever expanding allowing even more things to be added to the game via Behaviour pack. One downside of Behaviour packs are that they will disable achivements - there is no easy way around this.

How to install Behaviour packs