The document discusses conditionals and the zero conditional. It explains that conditionals have an if clause and a main clause, and whether a comma is used depends on the order of the clauses. The zero conditional is used for instructions and general truths that are always true. It expresses facts using the present simple tense in both clauses. Examples are provided to illustrate the form of the zero conditional. Practice exercises are included to reinforce using the present simple tense in if clauses for things that are always true.