Im sorry for being such a noob, but when looking around at different horns, many are described as more or less responsive than others. What exactly does "responsiveness" entail?
Thanks

Responsiveness to me is somewhat misleading unless describes what part of the instrument is less responsive. I guess if we're talking about it in general, you can think of it as a combination of how easily it blows, how quickly the note loads into the air column when you change pitch, and how easily that note notches. That is, how easily it plays.