Essentially, you're covered for any damage caused to your own vehicle and any third party damages, except in certain conditions laid out in your insurance policy.
These would include:
1) deliberate act - ie you set fire to your own vehicle
2) if you have an accident whilst under the influence of drink or drugs
3) theft by a family member, partner or spouse.
There are many more condition that could be applied, these tend to be the main ones.
The only real difference between this level of cover and TPF&T is that you're covered in the event of an accident, whereas on TPF&T you're only covered for a fire/arson or theft of/theft from claim. It also covers you for any third party damages (assuming you to be at fault)
TPO simply ensures that any third party claim (assuming you to be at fault) is covered - you are covered for no damage whatsoever to your vehicle.
That's not the be all and end all, but a tidy overview