This is the $(\infty,1)$-category $C \otimes D$ which is ‘the universal recipient of a bilinear functor’ from $C \times D$. Here, we think of coproducts in $C$ and $D$ as addition, and then if a functor $C \times D \to E$ preserves colimits in each variable, in particular it preserves coproducts and so is ‘bilinear’. Such a bilinear functor will factor uniquely (in a homotopic sense) through a universal bilinear functor $C \times D \to C \otimes D$, just like for bilinear maps and tensor products of abelian groups.