Puberty starts with a growth spurt, meaning you become quite a bit longer in a rather short time.
With girls the growth spurt normally starts between 10 and 11 years of age. You grow fastest when you are 12 and 13 years old; growth levelling off at age 14.
Guys’ growth spurt normally starts between 12 and 13 years of age. The increase in length peaks between 13 and 14 and normally levels off after 15.
Because girls start puberty earlier than guys they are taller than guys for a while and look more mature. This is one of the reasons they normally date guys that are a little older. This difference disappears at the age of 14 or 15.
Becoming taller often starts with the growth of your arms/hands and legs/feet, making you feel unattractive and clumsy for a while.