What is the meaning of "representation of an amalgam"? Let $\displaystyle \mathcal{A}=(A_1, A_2, B, \phi_1, \phi_2) $ be an amalgam. Then $\displaystyle Hom(\mathcal{A}, G)=\{\psi \mid \psi \mbox{ is a presentation of } \mathcal{A} \mbox{ into } G\}$.

So I want to know the meaning of "representation of an amalgam".