SilkAir is the regional arm of Singapore Airlines which had its humble beginnings as Tradewinds Airlines back in 1989. It was incorporated as SilkAir in 1992 and since then it has been operating regional flights spanning South East Asia, East Asia, South Asia and Northern Australia. It operates only narrowbodies (Boeing 737 and Airbus A319/A320). Recently, they have acquired 5 new 737 MAX as part of their fleet expansion programme.
Although fully owned by Singapore Airlines and one can earn/redeem Krisflyer Miles on SilkAir, it is not part of the Star Alliance group. What it means is that Business Class travellers cannot access Star Alliance Business Lounge using SilkAir boarding pass. Nevertheless, they can still access the Silverkris Lounge in Changi Airport Terminal 2 and designated SilkAir Business Lounges abroad.