Not quite nearly everyone has signed up to it though, you will find out all about it and its sodding annexs and when and where they had there conferences during your ground school.
An ICAO ppl is one from a country which has signed up to it and has its minimum standard the same or better than the ICAO minimum.
You can have compliant and none compliant in the same country. eg the UK JAR PPL is compliant but the NPPL isn't. And FAA PPL is but sports license thing they have isn't.