What is a guitar tuner?

Guitar tuners are necessary tools for a guitarist, most usage of these tools are for beginners, however after some time that you play guitar, you won't be needing guitar tuners, because you will be professional enough that you can tune your guitar just by hearing songs and notes and then you can realize the tunes on your guitar. But for now you can do something to make your guitar to sound better.

Guitar tuners can either be found as stand-alone devices (sometimes pedals) or some more advanced rack-mounted version. A guitarist or bassist can plugs his/her guitar into the guitar tuner through a cable and then play a note (in this case guitar tuner will show you which of notes are being played in your guitar).The mentioned tuners are powered by batteries or AC adapters.

There are also some software guitar tuners which also can be used to tune your guitar, and since there is no hardware,(but a pc which you already have) they can come cheaper or even free. Although the hardware tuners will be a lot accurate, the software ones are no useless.