What is a map file and how do I open a map file?
These files are called Quake Engine Map Files that refer to uncompelled game maps used by the game that Quake engines develop. These MAP files were developed by id software and are saved in a text format that humans can read. MAP files can either be a binary map file compilation used for Half Life and Quake games. Several map editors can be used to create MAP files like the Valve Hammer Editor, a program used to compile the map targeting it to BSP format. MAP files are also used by TorquePowered.com's Torque Constructor and they are used to transform maps to DIF formats that contribute to its development. These files can also be used for Torque games, targeting several platforms such as PC, mobile and console. MAP formats are used by numerous game engines like the Quake engines, Goldsource Engine, Unreal Engine, Torque Engine and Dark Engine. MAP files can be saved in newer VMF formats with the use of Valve Hammer Editor 4, a program previously called "Worldcraft”.
Relevant map file links:How to open map file on Youtube
How to open map file on Wikipedia
How to open map file on Microsoft.com