When you give someone props, you say out loud that they did something good — respect, credit, a public nod. “Props to her for finishing on time.” “You have to give him his props.” It comes from hip-hop and Black American English, cut down from “proper respect,” and young people far beyond that community use it now, on the internet as much as in the room. Though actually, this is informal street and chat talk, not essay talk. And it is not the theatre word: stage props are the cups and chairs on a stage (from properties). Same spelling, different life. Older, formal speakers may not use this props at all. You can also hear it as a little cheer on its own: just “Props.” meaning well done, I see you.