What is the difference between incomplete dominance and codominance?

The difference between the two is primarily the interaction of the proteins which are produced, ultimately dictated by the allelic behaviour occurring within the genes of the organism. Essentially, incomplete dominance is a certain kind of mode of inheritance where the heterozygous offspring produced from the mating of 2 separate homozygous parents would be an intermediate between the 2. So, the offspring only shows the phenotype of an intermediate one between the 2 completely different parents. No allele is dominant and masks the effect of the other. Co-dominance, occurs when the offspring produced from the mating of 2 distinct parents have both phenotypic traits of the parents. Yet in a unique arrangement. Basically, both phenotypes which were initially in the parents are showed within the offspring in a particular way.