When choosing a martial art there are often a few styles to pick from. Choosing the right style for you can help make your training better as well as make you like it more. Here are some of the most common styles and what makes them similar and different, too.
Karate. Most people think of karate when they think of a martial art. Karate comes from Japan (Okinawa) and literally means "empty hand." Of course there are weapons in karate but it was originally designed to be used without anything, so it was called karate. Karate uses different types of strikes including palm strikes, the side of the hand, the back of the fist, the fist, throws, and kicks. Different styles of karate will do things differently but most of them will have those. Karate has "kata" which are prearranged sequences of moves that are designed to illustrate combat scenarios. They are also used to help teach different applications. Many karate schools may spar, which is when two (or more) students practice fighting each other without knowing the ahead of time what the other one will do.
Taekwondo. This is a martial art that comes from Korea. It was created in the 1940's and was based on a few other arts. The name basically means "the way of the foot and the hand." Taekwondo is similar to karate in that it also uses hand strikes and kicks, but also involves a lot of high kick and jumping kick techniques. Because of this, people who practice need to develop good flexibility. Like karate, it involves prearranged sequences of techniques called "poomse" instead of kata. It also has sparring.
Kung fu. Usually used to refer to Chinese martial arts, "kung fu" is not technically a style of its own. Kung fu refers to a skill that was achieved through hard work, which can apply to martial arts as well as anything else. There are many styles of Chinese martial arts that can range from hard styles with punches and kicks, to softer styles that use more rounded moves. For example, imagine blocking your opponent's punch with a block using your own strength vs. blocking your opponent's punch with a move that pushes it out of the way. Chinese styles can be based on many different theories, and there are even some arts based on the close quarters techniques that were designed to be used on boats. Like karate and TKD, kung fu uses hand and foot strikes and has its own situations, and some schools will also spar.
There are other styles besides the ones mentioned here so you may find some that you like better than these, or one of these may be the one you want to study!