Execute is used when a sequence of functions need to be executed one after the other. It is typically of assistance in the HotDocs® converter.
Here is an (admittedly artificial, but useful for illustration) example:
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OnExitSet(Name,Number,Value,(),Execute(SetV('X',12),IncrementV('X'),GetV('X')),,EvenWhenNotEmpty)
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After the focus leaves the Name field, the Number data element will have its value set to 13.