
The books were made by liscensed professional authors. Those books were about halo NOT modding, tutorials, or any of that. Of course bungie had them made, they had to sell the authors thw rihts to the halo universe. Here:
A tag, in a game is usually either
a. a vehicle
b. a weapon
c. a scenery object
Tags contain all the data on one of those items. Such as projectiles (what your gun shoots) the projectiles speed the animations, and damage done to the object fired at. Or a vehicles speed or how it acts in the game.
Tags just put all the different models, effects (eg. a guns bullet flash), animations, and data into one file and use this file in the game.
Scenery objects are just objects that would be best placed in the game instead of modeled out of the map's bsp. Such as a rock or tree. Take the trees in sidwinder, if there was no such thing as secnery object and therefore, no rocks, trees, teleporters, vehicles, spawn points and etc. You can place any scenery object in the game using sapien (use HEK ( abbreviation for: Halo Editing kit)) which you will learn how to use in the HEK.
A mod (basic knowledge) is a just short for: modification. So when you mod a game you just modify its contents or they way things act or look.
A scenario is just a compilation of all the tags, scenery objects, and weapons put into one big file. It also includes the objects position in a map. Like say a tree was atop a hill at Z: 100 (up,down) X: 236 (left and right) and Y: -300 (forward and back). That would be included in a scenario file, and is editable.
a Bitmap is just a fancy drawing that is applied to a model or ground in-game. It is basically just coloring in the model or map with a crayon (quite literally).
A bsp is just a term for geometry in a map model. BSP = geometry = model = 3 dimensional object (or in this case, a map) created with a 3d modeling program.
What we mean by "Collision geometry" we mean, something is inside the box that the level is not supposed to be there and will impede flight and or moving around the map/model. Collision = something you can hit, or touch, geometry = surface, or ground or the model that is the map.
When yuo see something with the filename "YourFileName.bmp" , it is just an abbreviation for the files type. Like .bmp means bitmap.
Hope this helps.