What does a fixer do in a relationship?

I'm curious to understand, in the context of relationships, what exactly is the role of a fixer? Are they someone who constantly strives to resolve conflicts and smooth out rough patches, or is there a deeper meaning to the term? How do fixers navigate their way through challenges, and what qualities or skills do they typically possess that enable them to play this role effectively? Additionally, can being a fixer sometimes have its drawbacks, and if so, what are they?