diff --git a/compatibility.lua b/compatibility.lua
index fcf4660..7b32419 100644
--- a/compatibility.lua
+++ b/compatibility.lua
@@ -1,3 +1,6 @@
+-- Fix compatibility for settings-related changes
+-- Only loaded if the versions of the mod and the world mismatch
+
 local function version_is_lower(v1, v2)
 	local d1, c1, d2, c2
 	while #v1 > 0 and #v2 > 0 do
diff --git a/gridio.lua b/gridio.lua
index 4e1271b..af50803 100644
--- a/gridio.lua
+++ b/gridio.lua
@@ -1,3 +1,5 @@
+-- Input and output functions for grid maps
+
 local worldpath = mapgen_rivers.world_data_path
 
 local floor = math.floor
diff --git a/gridmanager.lua b/gridmanager.lua
index 84e00e2..be6cfdb 100644
--- a/gridmanager.lua
+++ b/gridmanager.lua
@@ -1,3 +1,5 @@
+-- Manages grid loading, writing and generation
+
 local world_data = mapgen_rivers.world_data_path
 
 local registered_on_grid_loaded = {}
diff --git a/heightmap.lua b/heightmap.lua
index 97fbd0b..8cffd38 100644
--- a/heightmap.lua
+++ b/heightmap.lua
@@ -1,3 +1,5 @@
+-- Transform polygon data into a heightmap
+
 local modpath = mapgen_rivers.modpath
 
 local sea_level = mapgen_rivers.settings.sea_level
diff --git a/init.lua b/init.lua
index b1ea6d0..8b227a1 100644
--- a/init.lua
+++ b/init.lua
@@ -1,3 +1,5 @@
+-- Main file, calls the other files and triggers main functions
+
 mapgen_rivers = {}
 
 local modpath = minetest.get_modpath(minetest.get_current_modname()) .. '/'
diff --git a/mapgen.lua b/mapgen.lua
index d565ea9..8f8f69e 100644
--- a/mapgen.lua
+++ b/mapgen.lua
@@ -1,3 +1,5 @@
+-- Mapgen loop and mapgen-related things
+
 if minetest.get_mapgen_setting("mg_name") ~= "singlenode" then
 	minetest.set_mapgen_setting("mg_name", "singlenode", true)
 	minetest.log("warning", "[mapgen_rivers] Mapgen set to singlenode")
diff --git a/polygons.lua b/polygons.lua
index 665b728..c67d659 100644
--- a/polygons.lua
+++ b/polygons.lua
@@ -1,3 +1,6 @@
+-- Fetch polygons from a given areas, and compute their properties
+-- and find to which polygon every point belongs
+
 local blocksize = mapgen_rivers.settings.blocksize
 local X = math.floor(mapgen_rivers.settings.map_x_size / blocksize)
 local Z = math.floor(mapgen_rivers.settings.map_z_size / blocksize)
diff --git a/pregenerate.lua b/pregenerate.lua
index 7b2d1b4..9dbf188 100644
--- a/pregenerate.lua
+++ b/pregenerate.lua
@@ -1,3 +1,6 @@
+-- Generate the grid using terrainlib_lua
+-- Only called on first mapgen, if there is no grid yet
+
 local EvolutionModel = dofile(mapgen_rivers.modpath .. '/terrainlib_lua/erosion.lua')
 local twist = dofile(mapgen_rivers.modpath .. '/terrainlib_lua/twist.lua')
 
diff --git a/settings.lua b/settings.lua
index a508b30..ba3d062 100644
--- a/settings.lua
+++ b/settings.lua
@@ -1,3 +1,5 @@
+-- Read global and per-world settings
+
 local mtsettings = minetest.settings
 local mgrsettings = Settings(minetest.get_worldpath() .. '/mapgen_rivers.conf')