As an English teacher, one is often asked about the conditional mood. My answer is to like to this article, which explains first, second and third conditional well enough to require no further elaboration. There is one conditional, however, that the article does not cover: zero conditional.

Zero conditional, which takes the form of declarative statements in the form "if X, then Y", is used to describe known cause-and-effect relationships. Examples include "if water is heated to 100 degrees Celcius, it boils" and "if people do not have access to clean water, they become sick". It is distinguished from other conditionals by both verbs being in the present simple tense.