Begonia is one of the largest genera of flowering plants, with well over a thousand species. The ones grown as houseplants are mostly foliage types, kept for spotted, swirled or metallic leaves rather than flowers.
What every Begonia wants
Bright, indirect light and humidity above 50%. They dislike direct sun, which bleaches the patterning.
Water when the top few centimetres are dry, and water the soil rather than the plant. Begonia leaves and stems are prone to fungal problems if they stay wet, so avoid splashing the foliage and keep the air moving around them.
Most Begonia are toxic to cats and dogs, with the tubers being the most dangerous part.