Describe all the following languages as a set of strings.

$L_3=L_1{L}_2$

$L_1{L}_3$

$L_3{L}_1$

$L_1{L}_2$

$L1\frac{O}{?}$

$L_1^R$

$L_2^R$

${\displaystyle \underset{?}{\overset{?}{}}}**$

$\frac{?}{\text{b}\text{a}\text{r}}(L_2)$

$L_1^0$

$L_1^1$

$L_1^2$

$L_2^2$