You are creating a pedigree to trace freckles, a recessive trait, in a friend's family. you find out

You can learn not only who shows the trait, in this case freckles, but you also can see who in the family is a carrier and who isn't.

You can find who has freckles and do not

Explanation:

From the pedigree you would find out both of the traits that one individual carries. From just looking as a family member not having freckles, it does not mean that they are not carrying the trait or that they could have kids with freckles. For example, if you see that your brother has freckles, but your parents nor you have them it means that your parents have a recessive trait for freckles and a dominant trait for no freckles. This means that if they both give the recessive trait to an offspring, the offspring would have freckles but if they have the dominant trait like you would because you have no freckles then you would not have them. So just by seeing someone's features with the naked eye, you do not get all of the information.

Well their body produces more melanin in the areas where they have freckles.

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.