diff --git a/bin/multi_unzip b/bin/multi_unzip
index f762ac9..94ecd3f 100755
--- a/bin/multi_unzip
+++ b/bin/multi_unzip
@@ -1,3 +1,11 @@
+#!/bin/sh
+
+# unzips the contents of every present zip archive into directories of the same name
+# the % is used to remove the file extension (.zip).
+# % matches the shortest occurence from the end.
+# %% would remove all extensions (.tar.gz would be matched by %%)
+# # and ## are the corresponding operators for matching at the beginning
+
 for file in ./*.zip; do
   dir_name=${file%.*}
   mkdir -p "$dir_name"