Welcome to MTTags.com. Hopefully, you'll discover that this a really easy place to find information about Movable Type Template Tags. If you think we could be doing something better, please let us know! If this is your first time here, be sure to stop by the information desk, because we've got a growing todo list that might already include what you were about to suggest.
A variable tag that provides a count of entries on the current blog that have the entry tag in context assigned to them. The tag context is created by either an MTEntryTags or an MTTags block.
Like all variable tags, you can apply any of the supported global filters to MTTagName to do further transformations.
Example code
Within an MTEntries block right before the entry byline, you might put:
<p>
This entry has been tagged (w/ entry counts noted):
<MTEntryTags glue=", "><$MTTagName$> (<$MTTagCount$>)</MTEntryTags>
</p>
See the relevant section of Chapter 5.4 in the User and Administration Manual entitled "Using Template Modules" for more examples related to entry tags, including the creation of "tag clouds".
Also, please see the important performance note regarding where MTTags lists are best placed for optimum performance, also in Chapter 5.4 of the User and Administration Manual, under "Eliminating redundant publishing".