What does the number 3 symbolise?

The number 3 is only a number and therefore does not symbolize anything.

Another Perspective Pythagorean number symbology says the number 3 is the first of unequals, it is the number containing the most sublime mysteries, for every thing is composed of three substances.

Numerologicly the number 3 is imaginative, energetic, bright, expressive, versatile, witty, successful, charming, ambitious, proud, lucky, commanding, seeks approval, over-extended, energies diffused. Actually three is very significant in pagan teachings.