Begonias are perhaps one of the most enduring and traditional houseplants you'll come across. They're easily loved but can equally be hated for being "old fashioned plants Grandmother used to grow".
Regardless, for the most part they're easy going, tolerant and somewhat forgiving of occasional poor care. The choice in variety is truly huge with close to 1000 species and thousands of cultivars. While almost all commercially grown Begonias are cheap to purchase some of the rarer varieties could set you back a little.
Broadly, the type of Begonia you can grow as a houseplant will fall into one of two categories. There are the foliage types, which are grown primarily for their aesthetically pleasing and unusual leaf shapes, colorings and markings. There are so many varieties and different looking foliage Begonias to pick from, so just choose the patterns you like best when purchasing.