An Augmented Triad is one that has the Major Third and a sharpened fifth.

As with triads that mess with the natural order of 'harmony' this triad produces a 'danger' or 'scary' type of sound. It has an intense flavor and would be used sparingly in the middle octaves. Another thing to understand is that this chord will not occur naturally in any key. The mysterious thing about this triad is that it will be replicated on guitar every four frets with a different enharmonic spelling with the same formation.

Augmented Triad: ROOT, M3, 5+

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The construction of the diminished chord is that we flatten the 3rd to create a minor triad then in addition we flatten the fifth creating the diminished triad.

Well, all bass players are going to come across a few these in their days and many won't even know what they are doing. A flat fifth is also know as something rather evil. Apparently it was a sin to play at some stage of our Christian history. Black Sabbath, although Christian, played the flattened 5th often. As it was a superstition that it would conjure the devil, sabbath would cloak their instruments, their clothing and their stage with crucifixes to ward off the evil. I'm not kidding about this.

Diminished Triad: ROOT, m3, ˚5