When you start mapping, you get lost about all the things that you can use in Hammer. To make you learning faster, you need to know what a map is. We will start to learn here some vocabulary and basic things, to understand what we talk about in the tutorials. A map is compound of two main things: world geometry, and entities. You need to place them, edit them, and when you have finished to create your map, you will compile it. The compilation convert your VMF map file, to a BSP file, that can be used by the game. The world geometry: It's all the basic that make the limits and the architecture of the map: the landscape, the ground, the buildings, are all created thanks to basic volumes, that can be brushes or displacements, where you will apply material. You need to understand, that you need your world to be sealed, thanks to the world geometry. Any leak in this seal, make the compilation fail with a "leaked" error in red. That's why even the sky, is created thanks to brushes! This gap in the world geometry leads to the void. That leak will result in a compilation fail... Brushes are simple volumes. They are composed of vertices (singular: vertex. There a the corners of a volume), sides, and faces (where you will apply textures). If the brush tool of Hammer allow you to create only cuboids, the other tools (vertex and clipping tools) allow you to edit them, and make more complex geometry shapes. Displacements are in fact, not volumes, but a face composed of many vertices. It's like a net, that you can more easily edit, like you was painting. Material is not geometry, but i class it here, cause it's associated to the world geometry faces. It's the texture you will apply on the displacement face, or on each face of your brush. If some are just textures, some others have special properties: some that will simulate water, some that will allow players to climb on it, some to simulate the sky, etc... The entities If the world geometry can allow you to create the walls, the ground, and the roof of a room, it will be empty without entities. These entities are more than simple geometry: they have outputs and inputs, that allows you to fire events, or handle them, to add dynamic interaction in your world. I will talk about only few of them. The brush entities. To create them, you will need to create first a brush, then convert it with the "toEntity" button of hammer... The triggers, that allows you to make players interact with the world, by simply touching them, like teleport the players, hurt them, or raise other kind of events. The function entities, that add functionality to brushes, like rotate or translate a brush, or acting like a button where the player need to press "use" key to start an event. The point entities: The lights. There is many kind of lights. That can be the sun (called light_environment) light diffused in all directions, or diffused in particular directions. The props, that are static, dynamic, or physically handled objects. They are based on models (complex geometry objects). Logical entities, like counters, timers, or condition handlers. Filtering entities, that allow you to make difference between humans or zombies for example ...And some last things... The last things we never talk about yet, are decals that allows you to add stickers on brush faces, and overlays that allows you to create grass for example... And that's all. I hope that this thread will help you to have a more clear vision of what a map is made of, and help you to discover by yourself what you need for your maps. Don't hesitate, if you have some time to waste (like in the bus or train), to navigate through the Valve Developper Community website, to discover more entities, and more in-depth about all of the art of mapping.