How to Build Simple Piano Chords -- 4 Type of Triads -- The "Root - 3rd - 5th" Approach 

You can build a triad by stacking two thirds... or by identifying "Root - 3rd - 5th". That is, by identifying the root note of the chord, and then defining the other two notes by their distance from the root note.
As you learn to build more complex chords, this will be a MUCH more useful way to think about them.