fixes #25343 by mentioning how collapse animates in docs

diff --git a/docs/4.0/components/collapse.md b/docs/4.0/components/collapse.md
index 86462492b2c3076c17e029cdb4158ae70b3823ef..01ebd52b7a4ebe912fc2f0298efd085b1c66d5a5 100644 (file)
--- a/docs/4.0/components/collapse.md
+++ b/docs/4.0/components/collapse.md
@@ -6,6 +6,10 @@ group: components
 toc: true
 ---
 
+## How it works
+
+The collapse JavaScript plugin is used to show and hide content. Buttons or anchors are used as triggers that are mapped to specific elements you toggle. Collapsing an element will animate the `height` from it's current value to `0`. Given how CSS handles animations, you cannot use `padding` on a `.collapse` element. Instead, use the class as an independent wrapping element.
+
 ## Example
 
 Click the buttons below to show and hide another element via class changes: