You could simply look up each of these arts in Wikipedia, which would also encourage you to spell them properly.
Brief capsules. Aikido was developed by Morhei Ueshiba as a sort of spin-off from Judo. It is designed to be a defensive style that uses the opponent's force against him. There are many different styles, some "soft", some "hard".
Hapkido is a Korean style that combines striking elements with various locks, chokes, and grappling techniques, as well as some weapons sets. It's designed to be a practical defensive art...
Silat is an Indonesian art with a variety of unusual techniques designed to work well in heavy, jungle terrain. It is related to some degree to Filipino styles but has a variety of unique techniques and also employs the traditional Indonesian weapon, the Kris.
Hwarang Do is Korean and was developed during a period in feudal Korea as a complete art modeled somewhat after the Japanese bushido. The "hwarang" were elite warriors drawn from the nobility and they practiced a variety of war-oriented fighting techniques.
All of these things have their uses.... And simply fighting is not the only reason for studying a martial art.
Others include physical fitness and health, the mastery of a difficult skill, competition, camaraderie, self-confidence, and even spiritual advancement.