The past tense (preterite) form is used in what is called the simple past, in sentences such as "We lit the fire" and "He liked to dance". One of the uses of this tense is to refer not to a past situation, but to a hypothetical (present or future) situation in a dependent clause: "If I knew that, I wouldn't have to ask." This is sometimes called the "past subjunctive", particularly in the case of "were", which can replace "was" in such sentences; see English subjunctive.