I've built a content type and added taxonomy to it. The user can choose one of the 10 terms from that vocabulary when they are building the content. On the node I want to build a sidebar that lists all the other nodes from this content type but filtered to be only the same taxonomy choice. I assume this is done through views but I can't figure out how to build that contextual filter that looks at the current nodes taxonomy.
To visualize what J. Reynolds said above.
Add Contextual Filter - Content: Has taxonomy term ID with following settings
then add contextual filter - Content:Nid (provide default value -> Content ID from URL) and in "More" section of that filter check "Exclude" checkbox, which will remove the currently viewed node from the list of nodes related by taxonomy term.