I'll begin by saying that, if you don't know the point of something, then no, you shouldn't use it. This goes for equipment, supplements, and a bunch of stuff.
Basically, a weightlifting belt can help you brace your abs/back/core to give you a more stable torso while lifting. This can help when you're lifting maximal loads (really heavy fuckin' weights) by helping you engage your abs to prevent injury and increase strength.
As a beginner, I'd say you don't need one quite yet, especially if your goals are more towards muscle size/fat loss than powerlifting/strength. Focus on building total body strength (which includes the abs, low back, and hips). Once you start lifting relatively-heavy weights with good form, you can consider using a belt occasionally.
Many (most?) coaches believe you can "build" your own belt through consistent ab/core work, which makes a weightlifting belt unnecessary in many cases. Do some reading, experiment in your own training, and eventually decide for yourself.