There are a couple of different types of Tuners that are available. The most common type is the clip on type. These tuners clip on to your headstock, and when turned on give you a readout of the note being played on the guitar. These are a cheap and effective way to tune your instrument. 

The second type is the metronome tuner combos. These are usually a rectangular black box. These have a microphone, a ¼” input, and a metronome. These will usually have a headphone output as well. These are a more comprehensive tool, useful both for tuning and practice. 

Lastly, there are pedal tuners. The most expensive type, these are for your pedalboards and are the biggest step up tuning wise. These don't have microphones, instead, they only take ¼” inputs, and only output via ¼”, in general. These are specifically designed for pedalboard use only.