The field taxonomy module allows you to do two things
1) Select taxonomy terms to attach to fields themselves.
This leads to such fields only being available for a node form if the node in question has already one of the selected terms assigned.
2) Select taxonomy terms to attach to values for taxonomy fields.
Both functionalities are currently not working with free-tagging vocabularies.
This module differs a lot from content_taxonomy. That module allows you to assign taxonomy terms to a node through a cck widget. This module does allow you to assign terms to either widgets themselves or to the multiple fields of a cck widget. It never assigns terms to a node.
Developed by Gerhard Killesreiter for Looforyoo SARL.