This is similar to saying saying "You've got it" or "You've got this", almost abbreviated from "you have got this under control" or idiomatically "you've got this in the bag" ( https://www.phrasemix.com/phrases/someone-has-got-something-in-the-bag ) . It is an encouraging statement telling the participant that they have got this situation under control, so to speak, and that they are going to do a great job as they are adequately prepared and have already made it this far.

Based on this context "You got it!" = "you can do this" = "you are going to have a great performance". But, "you got it" is used in many contexts. You can use it whenever you want to support someone. The other person may be shy, worried or not confident. Examples: A student taking an English exam --> "hey, don't worry. You got it". A work colleague is giving a business presentation --> "why are you worried? You got it" Sometimes, we also say "you got this". Even more casual --> "you got this man"/"You got this bro". You could say "you got this sis". But it sounds weird unless she is your sister :D Literally "you got it" --> means you are receiving something. But it is an idiomatic expression too.

Thank you for the kind explanations, Ophelia and Michael! So now I understand the expression may suggest largely two different meanings based on the context, signaling the start of the performance, or encouraging the performer.

If it's the last thing said before performer starts, it means "over to you". Or "Go". Or "Start now please." Or, more fully,"The sound system is now switching over to give you the live microphone." Or it could simply mean "You are great"; as Ophelia suggests, this really depends on context and the speaker's intonation and intent.

This depends on the context... If an MC says 'You got it' to a performer before the performer does something on stage, this can be said to the performer to reassure them that they have perfected their craft and that they essentially 'know what they are doing'. So the performer should feel confident because 'they have got it'. For example "don't be so nervous, you know what you are doing, you've got this". However if the performer is really nervous and 'struggling' before going on stage the MC can say to the performer "you got this?", the MC has asked the performer if they are essentially 'ok and ready to perform on stage'. I hope that this makes sense to you. :)