These FAQs are provided by the Vocabulary Knowledge Center.
The vocabularies are different in a number of areas including origins, format, license, and coverage. To see all the differences look at this comparison.
A copy of the NCI Thesaurus can be generated from the UMLS Metathesaurus using the MetamorphoSys tool that comes with the UMLS. The version of the NCI Thesaurus in the UMLS Metathesaurus will lag the current production release of the Thesaurus, so if timeliness is in issue for you, please visit the download center.
On the download landing page scroll down to the section on the NCI Thesaurus. There are several formats available for download: OWL, XML (both the inferred and asserted versions in a format suitable for use in Apelon DTS) and flat file. Decide which version you want and follow the link to the download page. You will be routed through a registration and then a license page before you come to the actual download page. You can register as a user if you want, but you don't have to. You do need to acknowledge the license terms and conditions (basically under the license you can do anything you want with the NCI Thesaurus content except to change it while still calling it NCI Thesaurus.)
The information you are looking for is about the UMLS Semantic Types which are part of the UMLS Semantic Network.
Follow this links for information on the Semantic Types.
This page provides a chart of the Semantic Types and their hierarchies: Semantic Types and Hierarchy.
If your question was not answered on this page, please start a new thread in the Vocabulary Knowledge Center forum for this terminology.