Stack Exchange network consists of 181 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
Q&A for work
Connect and share knowledge within a single location that is structured and easy to search.
I noticed two similar tags and I know about the tag-synonym thing but I can't figure out how to do it.
Its all explained here - it also says, as RegisteredUser said, that you need 2500 rep to do it.