There are basically three different types of guitar tuners. It is super important that you keep your guitar tuned, especially while you are learning to play, so you know when you are making mistakes or not. What I mean is that most of the time, if your guitar is tuned, you can tell you did something wrong because you can hear it. You can just hear that something is off. But if the guitar isn’t tuned, you may be doing everything perfectly and still think you are doing something wrong because that un-tuned guitar sounds awful. Keep that in mind.
When I say there are three different types of guitar tuners, what I mean is that they typically come in three physical forms depending on what you like or what you need. But, aside from how they look, I want to mention what they can do. A chromatic tuner can tune a string to any note you want it to. A non-chromatic tuner will only tune your strings to the the six notes in standard tuning (moving from the top, biggest string down to the bottom, smallest string, those notes are E, A, D, G, B, E). This is fine as you are starting, but there really is no reason to buy a non-chromatic tuner when you can get a chromatic tuner for around the same price and it is more versatile. There are different ways to tune a guitar (these are called alternate tunings) besides the standard tuning I mentioned and someday you may want to try some of these as you are growing as a guitarist. A chromatic tuner will allow for that. These two types tune one string at a time. A polyphonic tuner allows you to strum all the strings on your guitar at once and it will show you which ones are in tune and which are out of tune. These are a bit more pricey, of course, but are a pretty cool nonetheless.
These tuners typically have a rectangular shape and have a needle, or an image of a needle, on a screen, that moves when you strike the string. If the needle moves past the middle then you are “sharp” and need to loosen the string until it is in the center. If it is below the middle when you strike the string then you are “flat” and you need to tighten the string till it comes to the middle. These tuners usually have a small microphone on them to hear the sound when you hit the string. The disadvantage is that it needs to be quiet. Background noise can get in the way. However, most of them have a place to insert a guitar cable coming from your guitar so you can plug straight into it if you have an electric or an acoustic electric guitar and that eliminates the need for quiet while tuning. Some of these will also have a metronome setting so you can practice playing at a constant speed during a song.
These tuners clip to the head of your guitar and use the vibrations when you strike a string to allow you to tune the string. The screen is much like mentioned above but these are typically smaller and you can tune anywhere, noisy or not, since they are using the vibration of the strings rather than the sound. I just bought a clip on tuner because the new acoustic guitar I bought didn’t have a built in tuner. It works great and I really like it a lot.
If you have ever been to a live show and wondered how they keep the guitars in tune it is because you will rarely see a musician playing live use either of the two tuners mentioned above. They almost always use a pedal tuner. If you already know what an electric guitar pedal is then you will understand what I mean. A pedal tuner looks exactly like a pedal that you would step on or “stomp” to get a certain sound, whether distortion or chorus or you name it, to come through the amplifier. When you step on the pedal tuner it cuts off the guitar from the amp so you can tune quickly without being heard. It will have a dial or some lights just like the other two to let you know if you are sharp or flat and allow you to tune.
These are the three main types of tuners and what they will do. Remember to keep your guitar tuned no matter which type of tuner you decide to get. It will definitely help you as you are learning and you will know as you are playing whether you are doing something wrong or not.