Triads are very powerful, because they're literally in the air around us. Almost all vibrating bodies produce harmonics, and because of the laws of physics, the harmonics we hear most strongly generate triads - check out the strong harmonics at the 12th, 7th, 5th and 4th frets on your bass. We hear them almost instinctively. We'll work with major triads today.
Check it out: because of the "strength" of their distinctive sound, triads help "make sense" of your lines.