I'm not an English native speaker and I don't know how to pronounce $0^+$ and $0^-$.
Could you help me, please?
I'm referring to the symbols that appear for example in the limits $lim_{x\to 0^+}f(x)$ and $lim_{x\to 0^-}f(x)$. Thank you in advance for the help.
Those are right-sided and left-sided limits. You can say, as $x$ approaches $0$ from the right side, $f(x)$ approaches $L$. You can also say the limit of $f(x)$ as $x$ approaches $0$ from the right side.
Of course, the natural association of being to the left and right of a value depends on the dialect and language. You could use the notion of being below or above a value in place of mentioning right or left.