First and foremost, you have the right to access data stored about you. But, you also have the right to access the following information:
Purpose
What kind of categories of your personal data are processed?
data categories
What kind of categories of your personal data are processed?
Legal basis
What is the legal basis for the processing of your data?
Data recipients
Who (individual, private entity or public authority) has received your personal data?
Source
From which source was your personal data obtained?
Storage period
What is the envisaged period for which your personal data will be stored?
Logic of profiling
In case of profiling or automated processing, you have the right to know the logic, i.e. how the automated decisions are reached and what sources are used for making profiles.