${?}_{{?}_{{?}_{?}}{?}_{{?}_{?}}is\text{a}\text{s}\text{u}\text{b}\text{s}\text{e}\text{t}ofe-\text{c}\text{o}\text{m}\text{m}\text{e}\text{r}\text{c}\text{e}\text{t}\text{h}\text{a}\text{t}\text{i}\text{n}\text{v}\text{o}\text{l}\text{v}\text{e}\text{s}\text{e}\text{l}\text{e}\text{c}\text{t}\text{r}\text{o}\text{n}\text{i}\text{c}\text{t}\text{r}\text{a}\text{n}\text{s}\text{a}\text{c}\text{t}\text{i}\text{o}\text{n}\text{s}\text{b}\text{e}\text{t}\text{w}\text{e}\text{e}\text{n}\text{c}\text{o}\text{n}\text{s}\text{u}\text{m}\text{e}\text{r}\text{s}using\text{a}\text{t}\text{h}\text{i}\text{r}\text{d}\text{p}\text{a}\text{r}\text{t}\text{y}to\text{f}\text{a}\text{c}\text{i}\text{l}\text{i}\text{t}\text{a}\text{t}\text{e}\text{t}\text{h}\text{e}\text{p}\text{r}\text{o}\text{c}\text{e}\text{s}\text{s}\text{.}}$

$1.$

Business$-to-$business $(B2B)e-$commerce

$2.$

Business$-to-$consumer $(B2C)e-$commerce

$3.$

Consumer$-to-$business $(C2B)e-$commerce

$4.$

Consumer$-to-$consumer $(C2C)e-$commerce