If you don't know what tag synonyms are, you can just think of it like a website redirecting you, but instead it's a tag. This help page on the privilege of suggesting tag synonyms describes what happens when you ask with a tag synonym as one of your tags:
What happens when a question is asked using a synonym?
Any tags that match active synonyms will be automatically and silently changed from their original as-entered form to the tag that the synonym points to.
This also increments a synonym counter, which you can view at /tags/synonyms to evaluate the effectiveness (or ineffectiveness) of the synonyms that are in place.