If an individual has both a dominant and a recessive allele for a particular trait then that individual will have the heterozygous genotype and dominant phenotype for that trait.
Genotypes are the types of alleles that an individual contains for a particular trait. Alleles are alternative forms of a gene. These alleles are often represented by letter combination. Dominant alleles (the "stronger" allele) are represented by capital letters and recessive alleles (the weaker form of a gene) are represented by lowercase letters. Genotypes can be homozygous dominant (containing two dominant alleles), homozygous recessive (containings two recessive alleles), or heterozygous (containing one dominant and one recessive allele).
Phenotypes are the actual physical characteristics that are demonstrated by an individual. If at least one dominant allele is present, then an individual will show the dominant characteristic. Thus, both homozygous dominant and heterozygous genotypes will display the dominant phenotype. Homozygous recessive genotypes will display the recessive phenotype.