One of the many "Angelwing" Begonias. It will eventually make a bushy plant 3-4 feet tall, and about 2 feet wide. Many kinds have showy flowers, but some are just grown for their foliage.
In general, they like sharp drainage, but the potting soil should only dry out to about 1/2 inch deep between soakings. They like bright indirect light, and some kinds can take morning sun, or full sun if you are near the coast. As with most begonias, frequent, light feedings are in order, or a conservative dose of timed release food-low phosphate works best. South of San Francisco along the coast, or in the milder areas of the Coachella Valley, they can be used as landscape shrubs in the shade.

Thank you so much! :)
Going to bring it to my sunny work office and put it over a pebble tray for humidity.

That should work! Watch for mealybugs, their most common indoor pest. If it gets them, dab the bugs with a Q-tip dipped in rubbing alcohol, since, like all begonias, it is sensitive to insecticides.