diff --git a/Concepts.md b/Concepts.md
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+++ b/Concepts.md
@@ -62,6 +62,25 @@ An example tree could look like this:
 
 Storelocations should be defined down to the smallest possible location, to make finding the part again easy.
 
+## Footprint
+In electronics many components have one of the common components cases / footprints. The footprint entity describes such common footprints, which can be assigned to parts.
+You can assign an image (and an 3D model) as an attachment to a footprint, which will be used as preview for parts with this footprint, even if the parts do not have an explicitly assigned preview image.
+
+Footprints are a hierachically which allows you to build logical sorted trees. An example tree could look like this:
+
+* Through-Hole components
+    * DIP
+       * DIP-8
+       * DIP-28
+       * DIP-28W
+    * TO
+       * TO-92
+* SMD components
+    * SOIC
+       * SO-8
+    * Resistors
+       * 0805
+       * 0603
 ## Attachments
 ### Attachment
 An attachment is an file that can be associated with another entity (like a Part, Storelocation, User, etc.). This could for example be a datasheet in a Part, the logo of a vendor or some CAD drawing of a footprint.