Any organization that processes the personal data of people in the EU must comply with the GDPR. “Processing” is a broad term that covers just about anything you can do with data: collection, storage, transmission, analysis, etc. “Personal data” is any information that relates to a person, such as names, email addresses, IP addresses, eye color, political affiliation, and so on. Even if an organization is not connected to the EU itself, if it processes the personal data of people in the EU (via tracking on its website, for instance), it must comply. The GDPR is also not limited to for-profit companies.