The mapname.md file holds the mapInfoDef. This is where the script_entrypoint is located to load the starting point of the mapname.script file. This is also where the location, briefing, and campaign description is set. There are other parameters that are also setup here.
mapInfoDef mapname
{
data
{
"megatexture" ""
"gridsize" "256"
"script_entrypoint" "mapname_MapScript"
//Text
"mapLocation" "maps/mapname/mapinfo_location"
"mapBriefing" "maps/mapname/mapinfo_briefing"
"campaignDescription" "maps/mapname/mapinfo_campaign_description"
}
}