In Sannella and Tarlecki book "Foundations of algebraic specification and formal software development" they describe pushouts as:

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> Pushouts provide a basic tool for putting together structures of various kinds. Given two objects $A$ and $B$, a pair of morphisms $f:C \rightarrow A$ and $g: C \rightarrow B$ indicates a common source from which "parts" of A and B come. The pushout of $f$ and $g$ puts together $A$ and $B$ while identifying the parts coming from the common source as indicated by $f$ and $g$, but keeping the new parts disjoint.
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My question is about the last line. I understand that a pushout puts $A$ and $B$ together but I dont understand what they mean when they say that it's able to identify parts from $C$ and that it keep the new parts disjoint.

I understand that this is a very specific question, thank you for any help.