Stacking the C-major scale with thirds creates a chord progression  Play (help·info), traditionally enumerated with the Roman numerals I, ii, iii, IV, V, vi, viio. Its major-key sub-progression C-F-G (I-IV-V) is conventional in popular music. In this progression, the minor triads ii-iii-vi appear in the relative minor key (Am)'s corresponding chord progression.
If you're a fan of the Grateful Dead, check out the D'Angelico Premier Series DC Grateful Dead Semi-Hollow Electric Guitar. In the acoustic department, the Alvarez Artist Series AD60 dreadnought acoustic guitar comes highly rated, thanks to its hand-selected spruce top, mahogany back and sides, and powerful tone. Singer-songwriters and fans of acoustic-driven music must check out the latest Ed Sheeran Martin guitar, the comfortable, easy-to-play Divide Signature Edition Little Martin acoustic-electric.
The neck joint or heel is the point at which the neck is either bolted or glued to the body of the guitar. Almost all acoustic steel-string guitars, with the primary exception of Taylors, have glued (otherwise known as set) necks, while electric guitars are constructed using both types. Most classical guitars have a neck and headblock carved from one piece of wood, known as a "Spanish heel." Commonly used set neck joints include mortise and tenon joints (such as those used by C. F. Martin & Co.), dovetail joints (also used by C. F. Martin on the D-28 and similar models) and Spanish heel neck joints, which are named after the shoe they resemble and commonly found in classical guitars. All three types offer stability.
While four years old is a little young for formal guitar lessons, it's not too early to begin teaching your child musical concepts that will be important once they are old enough for guitar instruction at School of Rock. Your 4-year-old can participate in the Little Wing music program to learn fundamental concepts through fun, dynamic musical activities. 
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.