OCPP (Open Charge Point Protocol) is the open protocol that allows a charger from any manufacturer to communicate with a central management system (CSMS) from any manufacturer. In practice, it's the common language of the charging industry.
Without OCPP, each manufacturer locks you into its own management platform, so if you ever want to switch providers, add chargers from a different brand, or simply migrate to better management software, you're stuck. With OCPP, hardware and software are decoupled.
For a fleet operator or a business with multiple charging points, this has a very concrete implication: you can centralize management, billing, and access control for all your chargers — regardless of brand — on a single platform, and compare software providers without being tied to the hardware manufacturer.
When buying a DC fast charger, asking "Is it compatible with OCPP 1.6J or 2.0.1?" should be just as basic a question as asking about power output. It's the guarantee that your investment won't be locked into a closed ecosystem.