The Consultative Committee of 19 July 2021 decided that the Covid Safe Ticket (CST) can be used for events from 1,500 spectators upwards. The legal framework for that CST is laid down in an executive cooperation agreement (pdf) between the country's various authorities.
The Covid Safe Ticket is specifically intended to gain access to events without having to wear a mouth mask and keep a distance of 1.5 metres. The Covid Safe Ticket is only valid in Belgium.
Technically speaking, the Covid Safe Ticket and the European corona certificate are the same. Both work with a QR code, which automatically appears on your smartphone via the CovidSafeBE app.