What these suffixes do
The suffixes -ent and -ant are variants of the same Latin origin. They create adjectives describing a quality or state, and nouns naming people who have that quality or perform that action.
Adjectives: different, important, confident, patient, silent, violent.
Person nouns: student, servant, assistant, participant, resident.
-ent vs -ant: how to choose
Both forms are so common that there is no simple rule. Some hints:
-ent is more frequent: different, patient, student, confident, silent, violent, recent.
-ant also very frequent: important, assistant, pleasant, significant, relevant, distant.
In practice, if there is an -e verb as the root, it tends to be -ent (differ → different, confide → confident). If the root ends in -a or comes from Latin -are verbs, it tends to be -ant (assist → assistant, import → important).