Versetzen (parrying) is the simple action of stopping incoming attacks by blocking or cutting at them (such as we see in the Zwerchau techniques.
It should not be confused with the Vier Versetzen, which refers to a set of techniques for countering specific tactical situations.
Meyer differentiates between different types of Versetzen across his text.
The first type of parrying described by Meyer are parries which simply serve to stop the opponent's blow without achieving any particular advantage for yourself.
The second type of parrying is a parry which actively gains advantage for the opponent.
Along with these two applications of parrying are three broad structural approaches.
The simplest form of parrying is to statically parry the opponent's weapon. That is to say we move our own weapon into a position which just "blocks" the opponent's technique. For example, if someone cuts us from above we simply hold up our sword and catch it. These parries are mostly of the first category Meyer gives; they provide no special advantage in the follow up typically.
In his Dussack section Meyer says this is the least desirable form of defence as while we are protected, it leaves us vulnerable to follow up attacks, and places no pressure on the opponent (we fail to seize the Vor).
The next tier of Versetzen is to cut as our opponent cuts. If we do this without any advantage it is the first category of parry in Meyer, however we are admonished to always use these parries in the second way of parrying, that is with the intent of seizing the Vor with a follow up attack. The Krumphauw to the blade, for example, encompasses this kind of parry; we displace the blade with a strike and immediately wind in with a cut, slice, or thrust.
Meyer describes this as the most desirable of parrying movements. In this case we cut or thrust at the same moment as the opponent and in doing so we stop their attack with the same movement that we hit them. This is clearly of the second category of parry.
The classic technique of this type is Absetzen in which as your opponent cuts against you, your wind immediately into ochs against it and thrust to the face, catching his blade on the forte of your own and striking in a single movement.