I’m sorry for this awkward question, but I don’t know how else I should explain it, I tried to do some research online, but couldn’t find anything. For example, the notation looks like: $$\lim_{x \to 2^-}f(x)$$ $$\lim_{x \to 2^+}f(x)$$
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$\begingroup$It's just a way to know what limit you are going to find. When it has a minus sign at the top it means that you must find the limit when the desired $x$ comes from the left, meaning that you must find which number the limit goes as $x$ becomes more closer to $x_0$ from the left. Something similar applies to the positive sign meaning that you find the limit as you come closer to the number of the limit from the right.
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