The Explode button will break up the Selected Object into the individual segments that make up the object in Trace.The Explode All button will break up All Objects into their selected object into the individual segments that make up the object in Trace.
For example, a Rectangle will be broken up into Four Individual Lines which can be edited separately.
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Explode Tool Definition
In comparison, the Explode Allbutton will break up
the Selected Object
all objects into the individual segments that make up the object in Trace.