There really isn't a best age for kids to start guitar lessons, but most children under the age of 7 generally don't have the dexterity or patience needed to learn to play the guitar. With persistence and motivation some kids have learned to play guitar at some impressively young ages, but it really comes down to is the individual attitude and maturity level of the student. 
With so many options available in the world today, buying a guitar that perfectly represents your own style, tastes, and attitude has never been easier. Whether you're a classical guitarist looking for that perfectly balanced nylon flamenco, or a hard rock enthusiast who needs Pete Townshend crunch combined with Jack White power, there is simply no shortage of axes to choose from.
You don't have to be a virtuoso guitarist to touch people's hearts with your music! Guitar teacher Samuel B. shares a few of his favorite great-but-not-that-great famous guitar players... Towards the end of Johnny Cash's autobiography, you'll find the following paragraph: As to my musical future, my prospects look good. I can whack on a guitar as incompetently as I could a year ago, probably more so. I can sing just as well, or as badly, as I ever could. And I've got more songs trying to
Unlike many string instruments which use a bow to create a sound, guitars are played by plucking or strumming the strings on the instrument, which vibrate to create a sound. Chords are played when the guitarist holds their fingers down on more than one individual string to change its length, which in turn changes the frequency of the vibration created - in other words, it creates a different note. Performers often use guitar tabs, rather than sheet music, when learning music: this acts as a kind of 'map' to teach guitarists where to put their fingers on the strings.