A P60 is a record of everything you've been paid and all the tax and National Insurance Contributions taken out of it.  As for how to get a P60, they get sent out after the tax year ticks over on the 6th April, assuming you pay your tax through the Pay As You Earn (PAYE) system.  Your P60 is an important document to cling onto.  Whenever you need to prove what you've earned and what tax you've paid in a year, grab your P60 and it's job done.