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

They are know as heterozygous alleles.

Explanation:

Two IDENTICAL alleles are known as homozygous alleles.

I hope this helps you understand the difference, and as always, I am joyous to assist anyone at any time.

desert perennials often survive by remaining dormant during dry periods of the year, then springing to life when water becomes available. most annual desert plants germinate only after heavy seasonal rain, then complete their reproductive cycle very quickly.