It refers to a situation that may or may not happen depending on a condition. There are different ways to enunciate it, using additional works (like “might”) or the conditional or subjective verb tense, for example. It also may or may not use “if”. The structure of sentences can differ from language to language.
It is used in certain situations to express certain emotions, to give the idea that something is important or necessary, unreal or desirable, a possibility or an uncertainty. There are also certain verbs or adverbs that need to use the subjunctive. Its use depends on the context and may differ from language to language.