The five core numbers
Numerology reduces dates and the letters of a name to single digits (keeping the master numbers 11, 22 and 33). The Life Path number comes from your full birth date and describes your core direction. The Destiny (Expression) number comes from every letter of your name, the Soul Urge number from the vowels, and the Personality number from the consonants. The Birthday number is simply the day you were born, reduced.
We use the Pythagorean method, where A to I are 1 to 9, J to R are 1 to 9 and S to Z are 1 to 8. If you use a different spelling of your name, you will get different name numbers; numerologists differ on whether to use the birth name or the name you are known by.