ServiceMaster (NYSE: SERV) just spun off Frontdoor (NASDAQ: FTDR), and the newly public company should prove interesting to investors. The stock began trading on Oct. 1, and it's already had a bumpy history, rising to nearly $50 per share before dropping to less than $40 in the mid-October meltdown. The company sports a market cap of $3.4 billion, and ServiceMaster retains almost 20% of the stock.Who is Frontdoor?