Single live intrauterine fetus- one live baby
Of 21 weeks 2 days- that is the estimated age of the baby (plus or minus 2 weeks means the date could be wrong by about 2 weeks)
cephalic presentation- the baby's head is pointing down , unless baby changes position- the head will be delivered first- this is the way it is suppose to be
placenta fundal- the placenta is in the top of the uterus- if it were closer to the bottom there would be a risk of bleeding when the baby is born.This condition (where the placenta is close to the cervix
) is called placenta previa
Liquor is the fluid around the baby , it is said to be adequate.
The other measurements are telling you the baby's size, they would have used these measurements to determine the baby's age.
I hope this helps