I'm told you can "gig" frogs. But you can't "concert" frogs. So its different.

True.

Michael Buble, Carlos Santana, John Clarke, Al Marconi, Elton John, Boecelli, Manolo Escobar etc. I like Spanish stuff haha. I've been trying to learn flamenco for 2 years now. There are no flamenco guitar teachers where I lived. But I liked it so much that I just watched youtube videos where flamenco guitarists taught tidbits. I can do rasgueado and picado very well now.

I'm putting the gig/show/concert down in a medical school application and I feel that it has to be professional. So, I don't think I can put it down as a gig because it's slang. On the other hand, I can't put it down as musical performance because that's really vague and the admission committee is known for assuming the absolute worst possible scenario if you don't make things clear. eg. If I put publication in progress they assume I thought about publishing something but have yet to get started. So you see I'm afraid there might be some unseen loophole in musical performance.

Yes, I think you´re right, lancastel; "gig" is too informal to put on an official form. Maybe you can side-step the choice of word by using a phase like "played in public".

As a non-musician, I think of a concert as being an occassion where people go specifically to see an artist, generally stay for the whole duration, and maybe pay an entrance fee. To me, a gig could be a concert, but it could also be something less challenging, like playing in a bar or restaurant where people tolerate a bit of live music, but are really busy with something else.

Not sure why, but the word "gym" makes me think of people standing around for five minutes then wandering off down the corridor because they have a math class - so you might want to avoid using that word if you can.

good luck !