In Greek, verbs with an augment are translated into the past tense. In most cases, an augment is just an epsilon prefix (just like English past tense verbs have -ed as a suffix).
λυω = I loose (present tense) ελυσα = I loosed (aorist tense)
The imperfect and aorist tenses (both past tense verbs) have the augment (BBG 21.10). Augments only occur in the indicative (principle 13).