GDPR is the European Union's data protection law. It governs how any organisation, in the EU or dealing with EU residents, may collect and use personal data. Three plain ideas sit under it: have a good reason to hold data, collect only what you need, and respect people's rights over their own data.
For AI at work it matters because what you paste into a tool may be personal data. Know your organisation's policy before you share it. (This is general information, not legal advice.)