Being born in the Year of the Dog means the earthly branch of your birth year is 戌.
The Nature of This Branch
Xu earth is dry autumn ground and the storehouse of fire — the place of guarding and finishing. Deeply loyal; what it takes on, it carries.
Your Sign Is One of Eight Characters
Your zodiac sign is the earthly branch of your birth year — one of the eight characters in a saju chart. The character that stands for you yourself is a different one: the day stem (日干).
Two people with the same sign can be entirely different if their other seven characters differ. What the year branch really speaks to is your roots, your early environment and the impression you give.