IBM Rational Doors Importer
The DOORS plugin connects to the DOORS API (which is primitive unfortunately) and can extract the name, description and ID of the requirements only. The advantage of this importer is that it can repeatedly import the same data, performing updates. This makes sense if you are integrating with DOORS and need to keep the requirements in sync.
ReqIF File Importer
The ReqIF importer can import from an exported ReqIF format file from DOORS. This option allows you to import more fields from DOORS, including name, description, ID and any custom attributes. The importer will always append the requirements as new items, it cannot do updates. This is probably better for a one-time migration effort.