Visually, an Aasimar takes after the race of its ancestry, i.e., an elvish Aasimar would likely have long, pointy ears, and be a little on the thinner side.
Celestial Resistance
You have resistance to necrotic damage and radiant damage.
Mutation
As a Terran Aasimar, you are sometimes subject to rare mutations that manifest instead of your normal celestial abilities. Should you choose, you can take one of the following mutations:
Winged: Long feathered wings grow from below your shoulder blades, granting you a Fly speed of 40 feet.
Eldritch Blood: You can cast the Eldritch Blast cantrip, and your spell-casting modifier is Charisma.
Otherworldly Charm: Once per day, you can cast the Charm Person spell at 1st level, and your spell-casting modifier is Charisma. You cannot cast the spell like this again until the end of a long rest.
Light Bearer
As a being blessed by divine power, you can cast the Light cantrip, and your spell-casting modifier is Charisma
Age
Aasimar mature at the same rate as humans but live a few years longer.
Alignment
Due to their celestial heritage, aasimar are often good. However, some aasimar fall into evil, rejecting their heritage.
Size
Aasimar are built like well-proportioned versions of their ancestral race. Your size is Medium.
Darkvision
Thanks to your celestial heritage, you have superior vision in dark and dim conditions. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray.
Languages. Common, Celestial