TFS4JIRA Synchronizer is a web application accompanying JIRA plugin.
This component must be installed in order for TFS-JIRA issues synchronization to work. However, if you don't need this feature and TFS check-ins synchronization feature is enough for you, you don't have to install it.
Please review prerequisites list before installing TFS4JIRA Synchronizer.
TFS4JIRA Synchronizer installation process is quite straightforward. Simply run the installer (tfs4jira-synchronizer-setup-x.y.z.msi) as an administrator and follow instructions. The installer will warn you if any of the required components is missing (see this page for a list of prerequisites). TFS4JIRA Synchronizer application will be created under first IIS site bound to HTTP (80) port. If no such site exists, installation process will fail.
You should be able to access the installed application under the following URL: http://<your-iis-host-name>/tfs-jira-synchronizer.
TFS4JIRA Synchronizer application can be installed on any server machine that has network access to both JIRA and TFS and which is always online.