what about the gold?
It is given to customers who have reached a higher level of a member airline's frequent-flyer program.
Star Alliance Gold
Star Alliance Gold status is given to customers who have reached a higher level of a member airline's frequent-flyer program. 
is turkish airlines a member of the star alliance Yes, from December 2006. what is this alliance? The world's largest global airline alliance. why was it formed? UNANSWERABLE who were the members? VARIG, Ansett Australia and Air New Zealand. what is the silver category? It recognizes that you have shown a good degree of loyalty to Star Alliance member airlines and earns you two privileges that can make your journey smoother.
Star Alliance Gold status is given to customers who have reached a higher level of a member airline's frequent-flyer program Star Alliance Gold status is given to customers who have reached a higher level of a member airline's frequent-flyer program. Benefits are priority reservations waitlist, airport stand-by, check-in and baggage handling; an additional checked luggage allowance of 20 kg  and access to designated Star Alliance Gold lounges the day and place of departure with the presentation of a Star Alliance boarding pass.
Star Alliance Star Alliance Star Alliance
Star Alliance Gold Star Alliance Gold Star Alliance Gold
Star Alliance Gold status is given to customers who have reached a higher level of a member airline's frequent-flyer program. Star Alliance Gold status is given to customers who have reached a higher level of a member airline's frequent-flyer program.  Benefits are priority reservations waitlist, airport stand-by, check-in and baggage handling; an additional checked luggage allowance of 20 kg (or one extra piece, where the piece rule applies), and access to designated Star Alliance Gold lounges the day and place of departure with the presentation of a Star Alliance boarding pass.
wiki:19949625
Star Alliance [SEP] Star Alliance Gold
Star Alliance Gold status is given to customers who have reached a higher level of a member airline's frequent-flyer program. Benefits are priority reservations waitlist, airport stand-by, check-in and baggage handling; an additional checked luggage allowance of 20 kg (or one extra piece, where the piece rule applies), and access to designated Star Alliance Gold lounges the day and place of departure with the presentation of a Star Alliance boarding pass. Some airlines also offer preferred seating (an exit seat or a special section of the plane); guaranteed seating on fully booked flights, subject to the booking class code and notice period, and free upgrades in the form of a voucher, certificate or automatic upgrade at check-in.