The Sardana Device Pool is a Tango server establishing an abstraction layer for hardware access. The Pool has Controllers for device classes: Motors, IORegisters, CTExpChannels (counter-timer), etc. Controller instances are called Pool Devices. At DESY, Pool devices do not access the hardware directly, instead they are connected to Tango servers.
The MeasurementGroup is a selection of devices used for scans. It is part of a Pool.
The MacroServer is a Tango server executing Python scripts, aka Macros, that access Pool devices or other Tango servers. At DESY, there is a one-to-one relationship between MacroServers and Pools.
Doors are sub-classes of MacroServes. They serve as entry points for Sardana applications like spock.