What are the boundaries of different kinds of relationships?

So I’m a little fuzzy on the differences between friends, friends with benifits, situationships, relationships etc.

im currently really close friends with a guy. he's my best friend, the only person I really trust 100% and the person I feel the safest with. We both have feelings for each other but neither of us are in a good place for a relationship right now. There is also a lot of sexual tension and we flirt a lot. Not exactly sure if there’s a label for that. wouldn’t change anything between us I like how things are at the moment we’re both comfy in the relationship just curious what the label would be and what the differences are between different kinds of relationships as I don’t really know.

What are the boundaries of different kinds of relationships?
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