Well, to get our license we had to go through a 6 week training course like with every airline, and have the company exams at the end of each week. Provided that we passed these exams, we then had to go through the CAA written exams, with CAA examiners which were on sep, av-med, flight time limitations and geography (yes, geography!)
After passing the written exams, together with the others from my training course we had to go through the CAA practical examinations that took place on a company aircraft where we had to simulate an evacuation and actually blow an aircraft slide.
After succesfully going through that we are issued with our license with its endorsements that state what aircraft and aircraft variant we are trained on and licensed to fly as operating crew.
But for the license to be valid we need a valid Class C Medical Certificate. To obtain that we have to spend 10 hours in the Air Force Hospotal passing from every doctor and medical exams you cam possibly imagine! At the end of that day if you're lucky, you're issued with the Medical Certificate that needs to be renewed every 2 years for the licence to be kept valid.
Now, if one of us wants to change airline within the country and fly an aircraft that we're already trained on, we don't need to go through the whole 4-6 week training course. All we have to do is a recurrent course, basically sop's. Also, the endorsements are valid for a maximum of 2 years after which if we havent flown a specific aircraft type, we need to go through the whole training again.
I forgot to mention that once a year we need to go through a recurrent training.
Hope this answers some of your questions!