What causes layrngitis and is there any good way to get rid of it sooner than just resting your voice?

Many things. 'laryngitis' is not a diagnosis; it just means that the vocal folds (=larynx) are inflamed and this shows up as a poorly functioning voice. Rest will almost always improve things if the underlying cause is use-related but, there can be other causes. If you lose your voice often, go see a laryngologist who will examine your voice and talk about your voice use habits to make a plan with you.
Viruses. Viral infections cause the majority of laryngitis. Resting your voice is good but not always possible. Avoiding very hot/cold liquids and hard food may help alleviate some discomfort. I find that inhailing tepid mist from a humidifier mixed with eucalyptus oil helps me treat it. Eucalyptus oil sooths the inflamed mucosa, whereas mist helps relieve the dryness and tearing pain caused by inflammatio.