a coach sent me an email and asked if i could possibly attend a recruiting weekend. what is this?

If it is not a high price camp, it could very well mean that they have some level of interest in you.

If it is not an official visit, it could be a recruiting tool to spark interest and get you introduced to the school.

I have not heard that exact title, but some schools have what they call Jr days where it is basically a unofficial visit where they invite you to come see a football/basketball game or baseball scrimmage, take a tour of the school, visit exiting players and coaches.

Another program may have you do the above things and also have you pay a very small fee for recruit camp to let you workout on the field in a showcase format to sell you on the program.