Definition Let $\mathscr{L}$ be a first-order language and let $\mathcal{K}$ be a class of (possibly finite) $\mathscr{L}$-structures. $\mathcal{K}$ is said to have amalgamation property (AP) if for every $A,B_1,B_2\in \mathcal{K}$ and every $\mathscr{L}$-embeddings $f_1:A\rightarrow B_1$ and $f_2:A\rightarrow B_2$ there are an $\mathscr{L}$-structure $C\in\mathcal{K}$ and $\mathscr{L}$-embeddings $f_1^*:B_1\rightarrow C$ and $f_2^*:B_2\rightarrow C$ such that $f_1^*(f_1(a))=f_2^*(f_2(a))$ for all $a\in A$.
I saw the phrase “type amalgamation” in this thesis so my first question is:
Question (1) What does type amalgamation mean?
Definition A complete first-order theory $T$ is said to be simple if each type does not fork over some subset $A$ of its domain where $|A|\leq |T|$.
Also in the mentioned thesis the author talks about types amalgamation in simple theories which does not make sense for me. So my second question is:
Question (2) What does type amalgamation mean in the context of simple theories? and what are its properties?