As the name implies, this scale is made up of whole tones. A tone is simply the distance from one note to another note two frets above or below your original starting note. eg from G to A on the first string.(3rd fret to 5th fret). From the construction of this scale, 1 3 (#4 or b5) (#5 or b6) b7 we can see that the 1 3 and b7 are the same intervals which exist in the dominant 7th chord.
The fifths however have been altered by being lowered (b5) or raised (#5). What this means, is that if we were to play this scale against a regular 7th chord the raised and lowered fifths would clash with the unaltered fifth in the 7th chord. This scale therefore is mostly suited for use with dominant 7th or 9th chords which have either a raised or lowered fifth . eg 7b5 , 7#5 or 9b5 , 9#5 chords. The Whole Tone scale is also a good choice for most augmented (+) chords. The plus sign + signifying the raised 5th in the chord. For either 7b5 chords or 7#11 chords the 4th mode of the Ascending Melodic Minor scale is another option.
Whole Tone scales are a lot of fun to play on the guitar as they provide so many different patterns and shapes which are easy to remember. Using the 1st 2nd and 4th fingers enables us to quickly play whole tone runs all over the neck to create some very off the wall riffs. Just what you might need to add some interesting twist to your solos. Be carefull though to keep things in context with what you are playing. Your solo should still flow logically from one idea to the next, the scale choice simply being a vehicle to melodically move around in. Don't just think " ah I'll just throw in a few whole tone riffs now" in the middle of your solo, or it will just sound disjointed. The choice of notes should always be led by your ear, not your fingers.
It is important to note that any note in a Whole Tone Scale can be considered the tonic, and that there are really only two Whole Tone Scales available, eg the F, G, A, B, C#, and D# Whole Tone Scales all have the same notes as do the F#, G#, A#, C, D, and E Whole Tone Scales.