Personal data covers data that could directly or indirectly identify a person.
Under GDPR Article 4 (1) personal data is defined as follows: any information which is related to an identified or identifiable natural person.
In practice, this covers a very wide range of data, including:
Name
Address
Location
Online identifiers, including:
IP address
Tracking cookie or equivalent
Health information
Income
Cultural profile
And more
Source: European Commission.