A glossary is a lexica that contains terminology to be used or not be used in the translations. It's here to aid human translators to use the terms preferred by your organisation.
Enabling the glossary feature
You can enable the glossary by uploading a glossary file on your project's setting page:
Currently, both tbx and utx glossary files are supported.
Using the glossary
In the focus view, on every segment on the right side you will see the terminology based on the source text (suggestions for term usage) and your translation (approved term usage, suggestions for alternatives):
The terms will be checked on every change of your translations.