Agree with Shoveit and there are MANY threads on this topic that you can search. Fall and Winter camps are largely fundraisers for the program and the assistant and volunteer coaches. That said, mileage varies. Some schools will use these as opportunities to bring in guys they are already talking to for another look or a first in-person look. Two of my son's colleges did this with some regularity. Some schools don't travel much and pull primarily from local talent and, therefore, will actually be looking for guys. Although they will generally be surprised to find any strong local talent they are not already familiar with.
Of course, there is the instruction aspect. Typically, there will be college assistants doing the lions' share of the work and instruction. For a young HS'er, this can have value. Occasionally, the HC is involved. Many are hosting at their own school and there are no other colleges involved while some bring in multiple schools.
I would say that a player should not have expectations of being recruited or discovered unless they have meaningful dialog prior to the event. It can be worthwhile otherwise for the instruction but that is typically very much surface-level depending on the size and length of the camp.
One potential pitfall of these camps that occur over Holidays is that many players are in the middle of (or end of) arm shut-down. You don't want to interrupt that rest and try to execute hard throws if the arm isn't ready for it.