What does it mean if there are two different alleles for a trait ?

The trait is heterozygous.

Explanation:

Heterozygous: "Having two different alleles of a particular gene or genes."

A heterozygous genotype looks like: Rr. The capital R is a dominant allele, and the lowercase r is a recessive allele. These two alleles are not the same (not two dominant alleles or two recessive alleles) meaning that the trait is a heterozygous trait.

The opposite of a heterozygous trait is a homozygous trait, in which both alleles are the same (both dominant or both recessive) and can look like RR or rr (genotype-wise).

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.

i don't know. if i were you, i would search it up online : d