It's a good leaflet.
If you Google 'cancer staging', do add 'prostate', as each cancer group has its own staging system, though almost all are based on the international TNM model.
Do ask your doctor (or the Specialist Nurse) what your TNM score is. It'll be there in the notes, even if they haven't thought to mention it to you, though it's quite possible they did, and amongst all the other stuff you were hearing, which was more 'real world', you might have missed some technical jargon that wouldn't have meant much! Research has shown that people only hear a little over half of their key interviews - when taped and played back, people are shocked at how much they missed!
From what you've said before, it sounds like T3a/b N0 M1:
The tumour has broken through the capsule, but it seems not to have spread to neighbouring tissue. It has spread to bones.
T is an assessment of the primary Tumour, in a range from 1 to 4
N is a measure of direct spread to local lymph Nodes
M refers to Metatstic spread - eg to bones.
It is very important, as it will determine what treatment options are open to you, if intervention is needed. It also allocates you to one statistical group - instead of asking 'what's the outcome Doc', you can ask 'I'm T3bN0M1, what's my likely outcome'. It makes them squirm, but you tend to get a better interview. Caution: Never ask unless you can cope with the answer! I'm cursed, I can't cope without the answer!
If they are unsure (a or b), it's better to assume the worse option. I was diagnosed with T3N0M0 (no-one mentioned the 'a' until I asked), and the surgeon took the line "A lot of 3s turn out to be 2s when we operate"; I asked him how many 2s turned out to be 3s, and he looked suitably embarrassed. Staging is very important, but not a perfect science; it is limited by the quality of scans; much better these days, but not perfect.