You are creating a pedigree to trace freckles, a recessive trait, in a friend's family. you find out which of her family members have freckles and which do not. when you complete the pedigree, what can you learn about members of your friends family that you could not tell just by looking at them.

You can find out that they have the ability of giving the trait of freckles even if they do not have them themselves these people are called carriers

You could tell what people (that don't have freckles) were carriers of the recessive allele or not. Since you can only tell that people with freckles are homozygous with recessive alleles, and you can only tell that people without freckles are either heterozygous, or homozygous with dominant alleles, a pedigree will tell you about their genotype, instead of guessing based on their phenotype.