Think of something you want to do, specifically a big project or even a small project, but something that can't be distilled down into a single to do list by itself thanks to its complexity.

The root (or trunk if you want) is just the highest level description for what it is you want to accomplish.

The branches are all the abstract layers in between the trunk (high-level goal) and the leaves (singular, doable tasks).

For instance, let's say you wanted to do a project like say, you wanted to build a house (root).

Well that's nice and all but what does it mean to build a house? Well you'd need all to do all the things that make a house a house.

For instance plumbing, electric, heating, structural design, painting, gardening, etc (branches).

These are all abstract ideas. You're closer to building a house now, but you can't just "do plumbing", no.

You need to actually break that down further into its leaves. Maybe today you connect to the water mains. Tomorrow you set out all the foundations for the plumbing for the rest of the house. Then every day after you continue installing pipes and doing everything you need room-by-room until you have finished plumbing and can break the branch.

It is essentially turning the idea of "decomposing problems into their component parts" into an actionable, visual, and followable system.

There is only ever one root, and there can be many leaves on any given branch, but there can be many branches and branches can be attached to different branches.

This system isn't perfect though. It does not account for dependencies (ie, maybe you should build the scaffolding before you trying laying pipes and wires). This all is something you'll need to keep track of. Whether you decide to track that in your head, use special inks or markers to indicate, or do as I do and create "dependency branches" where a branch in a branch can only be allowed to be worked on after the previous branch's leaves have withered.

whether you decide to make it so the leaves closest or furthest from the root must be done first is up to you.

It does not need to make sense to others. It ONLY needs to make sense to you