Heres a small breif of what each does.
.sqm.sqm files (or shall I say file (mission.sqm)) is found in all missions, and is the only file of its type. This file contains all the data about the mission contents, for example: Where every object is, whats in its init line etc... basiclly what you see in the Mission Editor is in the mission.sqm.
.sqsScript files. If you want something done in ofp, and it isnt a basic trigger script then you would put it in a script. Scripts are executed in many ways including triggers, other scripts, and units.
.sqfThese type of files are functions. I cant explain these that well since ive never used them but I do beleive that it process the function and then provoids an output for a script. Read more about .sqf files
HERE.
Description.extThis file is also executed early on. It isnt a script, but kind off a config file for a mission. If you want custom sound, music or text it is defined in this.
init.sqsAs you know from what you have read above, the init.sqs file is a script file. The diffrence with this is that its one of the first things that happens when you launch a game. As soon as you leave the player assignment screen and click ok, the init.sqs is started just before the breifing.
Other Mission Files and Content.jpgI wont go into to much detail, but you will reconise a .jpg as a picture. As explained breifly earlier, it is defined in the Description.ext file.
.paaYou probably dont reconise this, but it is also a picture format that was made by BIS which can be read by OFP. You can get programs (Check the tools section on OFPEC) to view and convert jpg files to this format. If you had a lot of time, it would think it would be a good idea to use .paa instead of .jpg. For more information check the
BIS Wiki site HERE.
Folders UsedIn missions you can use folders, but this really isnt a thing I can tell you much about because I havnt used folders for much. I have however used folders for music/sounds in missions.
Sound and Music FoldersA folder named Sound in the mission folder is, to beleive it or not, the folder used for all your sounds (effects, voice overs etc).
A folder named Music in the mission folder contains music.
Sounds can be either .mp3, .wav , .wss . (These are the sound files you can use that I am aware of anyway).
Each sound file is defined in the Description.ext
For more information about using Sound/Music in a mission, check
This Tutorial Out.
Hmmm I think i've covered most things, and everything I know