PGO stands for Personal Health Environment.

This is an app or website where you can view a copy of your medical records for free. Sometimes you can also add data yourself, such as your blood pressure or weight.

There are various PHRs which you can choose from.
Not all healthcare providers participate yet, but more and more are. Also, you cannot yet enter all data into a PGO. But that is changing.
Via this website, you can check whether your healthcare provider can be found in a PGO:

MedMij Healthcare Provider Register

With a PGO, more and more health data is stored in one place. This gives you more control over your health.