wrap days are where normal 'days off' in your roster are added either side of leave to give a longer time off.
Just like an office worker gets. - if you work a 9-5 5 day week, then if you take 5 days leave, you get 9 days off - 1 weekend, 5 days leave, another weekend. As any of the 365 days per year can be work days for us, weekends and bank holidays have no particular meaning. Therefore if I take 5 days leave I get 2 days off alocated before hand, and 2 after.
if I take 10 days leave I get 2 days off, 5 days leave, 2 days off, 5 days leave, 2 days off etc etc.
These are called 'wraparound' days off.
The other question should be self explanitory - 5 on 4 off means just that - work 5 days, have 4 days off,.
Common ones around in various airlines are 5/4/5/3, 5/4, 6/5, however most airlines have 'random' rostering so that there is no fixed pattern.