diff --git a/README.md b/README.md
index 0bbbbc3..7e1e859 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,14 @@
 # SQL2CSV
 
 Convert MySQL SELECT to CSV format
+
+## Folders
+
+### Input
+
+'input' folder is for .sql files containing QUERYs. Query must be correct, isn't modified in any way (directly executed, as is). Must include SELECT.
+Make sure the input is save, it's directly executed and not checked for anything.
+
+### Output
+
+'output' folder is for .cvs files. Output of sql2csv is written to the folder, the name of the file is same as input file except .sql is changed to .cvs.