This is one of the many versions of the LGB 5008 transformer.
This one from around 1970
It has a 14 volt,1 amp AC output for lights and such and also a fixed 14 and 17 (or 18) DC output.
There is no reverse switch.
The DC output of this unit is meant to connect to an LGB 5010 or 5012 throttle which will provide the speed control and the reversing.
As to the 14 and 18 volt switch positions...
When LGB started in 1968, the DC power packs were 14 volt units.
18 volts was introduced to help run the trains outdoors where with long runs one would get voltage drops on the rails, so a higher voltage was needed.
Eventually LGB settled on 24 volts as the maximum DC voltage and it's still that today.