Two brush dynamos can be wired in several different configurations but as far as automotive applications are concerned, the vast majority of them are wired in one of two different ways referred to as 'shunt' and 'series' configurations. Some manufacturers such as Lucas preferred 'shunt' and others, notably Bosch, chose to use 'series' so both configurations are common place.
In the pictures below, only the parts involved in wiring up the required configuration are shown. Along the bottom of each picture are the field coils. In this case there are four field coils wired in series so that the end of one coil is connected to the start of the next. This means that , however many field coils there are, there will be two field coil connections - shown as two brown wires. Above the field coils are the two brushes which would bear on the commutator on the rotating armature (not shown). Each brush has its own tag wire. So we have two field coil connections and two brush connections.