Ex d indicates that the equipment uses the Flameproof method of protection - it can withstand an internal explosion without causing ignition of the external atmosphere. Ex e indicates that the equipment uses increased safety protection - it uses high-integrity construction to minimise the chances of a spark or hot spot acting as a source of ignition.
Ex de indicates that the equipment uses both types of protection in some combination - it may be that the main method of protection used is Ex d but has, for example, an Ex e terminal box - this is relatively common with motors. You need to check the detailed certification documents for more information.
To add: If a Ex e Juntion box or control cabinet is used then the internal non switching components can be Ex "e" rated, and any switching device like MCBs shall be rated for Ex "d" and marked as Ex "de".