# What is meant by the notation $L(…)$?

I am currently studying about formal languages and automata. I am trying to solve a problem but there is a notation whose meaning I'm not sure of.

I have a question to find out the relationship between two languages $L_1$ and $L_2$:

$L_1:$

$S \to aSa|bS|e$

$L_2 \to L((ab+ba)^*)$

My question is, does it mean that $L(ab+ba)$ is the set $\{ab, ba\}$?

I mean, $L(ab+ba) = L(ab)\cup L(ba)$

This link confirms my intuition that $L(R)$ where $R$ is a regular expressions simply means "the language produced by the regular expression $R$".

In that case, $ab \in L_2$ but $ab \notin L_1$