diff --git a/src/mechanize/form/button.cr b/src/mechanize/form/button.cr
index 8a610bf..4a55eda 100644
--- a/src/mechanize/form/button.cr
+++ b/src/mechanize/form/button.cr
@@ -1,3 +1,5 @@
+# This class represents button related html element.
+# <button>, and <input> whose type is button, reset, image, submit.
 class Mechanize::FormContent::Button < Mechanize::FormContent::Field
   getter form_node : Node | Lexbor::Node
 
diff --git a/src/mechanize/form/image_button.cr b/src/mechanize/form/image_button.cr
index 1cd1d68..583f39d 100644
--- a/src/mechanize/form/image_button.cr
+++ b/src/mechanize/form/image_button.cr
@@ -1,2 +1,3 @@
+# This class represents <input type="image">
 class Mechanize::FormContent::ImageButton < Mechanize::FormContent::Button
 end
diff --git a/src/mechanize/form/reset_button.cr b/src/mechanize/form/reset_button.cr
index baa3970..a5385e7 100644
--- a/src/mechanize/form/reset_button.cr
+++ b/src/mechanize/form/reset_button.cr
@@ -1,2 +1,3 @@
+# This class represents <input type="reset">
 class Mechanize::FormContent::ResetButton < Mechanize::FormContent::Button
 end
diff --git a/src/mechanize/form/submit_button.cr b/src/mechanize/form/submit_button.cr
index 691da00..90aa146 100644
--- a/src/mechanize/form/submit_button.cr
+++ b/src/mechanize/form/submit_button.cr
@@ -1,2 +1,3 @@
+# This class represents <input type="submit">
 class Mechanize::FormContent::SubmitButton < Mechanize::FormContent::Button
 end