Types of Tuners
First let's talk about some of the most common types of tuners we use. In our very first tutorial I played my open strings on at a time, and you used your ears to match the pitch of your string to my string. You can find online tuners that do the same thing, where you click on a string and then you match your pitch to the sound it makes. This works, but it's a bit cumbersome.
Instead I most often use what's a headstock tuner. It's called that because it attaches to the headstock of your guitar. From there, it picks up the vibration of the guitar and somehow it's able to pick up the exact pitch from that. This is really practical, because it's not affected by the noise in the room. We'll talk about how to read it in a little bit.
Another common option, at least for playing at home, is to use an app like this one. You can get a great tuner for your smart phone for just a couple of bucks. These apps pick up the sound of your guitar through the microphone, so they can be hard to use if you're in a noisy environment.
You can also buy a tuner that's a separate device. This one also works through a microphone, or you can plug a cable from your guitar into it. To connect through the cable it of course requires that you have a pickup system in your guitar, like you do on an electric. If you're playing an acoustic you may not have a pickup system. In that case you'd have to use the microphone or a headstock tuner.
Finally, here's what's called a pedal tuner. This one is most common when people perform live on a stage or in a rehearsal room with a band. This one does not have a microphone built-in, so you have to connect to it with a cable. You step on it to engage it, which typically mutes the sound and allows you to tune without everyone having to hear your tuning notes. This is really only necessary if you want to play loud on a stage or in a rehearsal room.