My phrase is, in specific, “real” or “so real”. This is not necessarily a description of reality but more a one-word response or insert meaning “what you’re saying/experiencing/feeling/this event/etc. is real to me and is valid”. 

As is important to note with this (and with all phrases that are widely used on the internet): this phrase is not always used the way it’s intended to be and is, like all things on the internet, heavily steeped in irony. Much like how people will ironically say “you’re so right” to someone who they patently disagree with, someone on the internet might say “so real” to something that they do not agree with or find funny.

This is a phrase widely used in the queer community but taken (like many phrases in the queer community such as "yaass" "slay" or "periodt") from the black American language community.