The most important chords
There are a lot of different chords. This includes basic major chords, suspended chords, and many others. Three chords are essential to know. Without knowledge of these primary chords, you will not be able to play some of the songs you want to. On the other hand, once you know how the three chords work, you will have the ability to play thousands of songs. This includes rock, pop, country, folk, blues, gospel, and other styles of music.
The primary chord formula
The major scale can be used to figure out the primary chords of a given key. As an example, in the key of C, we would use the C Major scale. It's notes are C, D, E, F, G, A, and B. The formula is I-IV-V. This means we take the first, fourth, and fifth notes of the scale to figure out the primary chords in the key of C. They are C, F, and G. When you play the C, F, and G chords, you are playing the three primary chords in the key of C. You can play literally thousands of songs with only these chords. Please note there are no sharps or flats in the C Major scale.
The significance of I-IV-V
When you think of all the songs you might want to learn, the odds are quite good that part of them will fall into some variation of this primary three chord structure. It doesn't matter if your playing guitar, piano, or some other instrument. It all works the same.
If you sit down to work on a song, a major part of your effort concerns what chords to use. Once you understand the I-IV-V formula, you will be ahead of the game in most cases. Of course, not all songs are played with this formula, but it is probably the most popular chord progression ever.
I-IV-V sounds great to most people. If your playing a song in the key of C, and the first chord is C, there is a good chance the next chord would be either an F or G chord. This will really help you figure the chords of a given song that was written in the I-IV-V formula.
It is important to remember the primary chords are the I chord, the IV chord, and the V chord, based on the scale of that particular key. This formula has been around for a very long time. Artists who have implemented the I-IV-V formula include Mozart, Chuck Berry, Johnny Cash, The Beatles, and even Van Halen, just to name a few.
Being a musician is a journey. Knowledge is cumulative, and acquiring a strong foundation of musical knowledge will help you become the best you can be. Learning the I-IV-V formula, and how the primary chords work together is an important bit of knowledge. This will definitely add to your overall musical foundation.