Noun Phrase/adjective from Latin: "something in place of/(in exchange) for something." Implies a reciprocal or mutual exchange relationship. Note, the Latin does not mean "What for What."
Noun Phrase: "He stole my bike, I stole his boyfriend, I'd call that quid pro quo."
Adj.: "'I scratch your back, you scratch my back' implies a quid pro quo relationship."
Quid Pro Quo in context:
"I want you to do us a favor though" -President Donald J. Trump in regards to releasing the Congress-approved military aid to Ukraine.