In Minitek Smart Search, a branch is a group of content maps that belong to the same map type. For example, take a look at the following image:
As you can see in the image above, we have created a Filter of Content type: Articles and we have selected 6 content maps for this filter:
The first 3 content maps
are all authors, therefore they belong to the same Author branch. This branch will automatically get the label: COM_MINITEKSMARTSEARCH_FILTER_BRANCH_AUTHOR_1. It's up to you to translate this text string as you prefer. You can do that in Extensions > Language(s) > Overrides.
The other 3 content maps:
are all Joomla Categories and form a Category branch with the label: COM_MINITEKSMARTSEARCH_FILTER_BRANCH_CATEGORY_1.
Minitek Smart Search auto-detects the content maps, automatically places them in different columns and creates different labels for each one of them.