For me, a keyboard qualifies as a gaming keyboard if it has some anti-ghosting or
NKRO feature that enables simultaneous keypresses of keys typically used in games, e.g. SHIFT+SPACE+W at the same time, and other similar combinations. Logitech G910 is essentially NKRO.
Some other features found in G910 and other gaming keyboards:
- programmable and macro keys (I've never found much use for them)
- in recent years, mechanical switches have become very popular and tend to be included under the "gaming" umbrella term, even though many non-gaming keyboards also have mechanical switches (especially Cherry MX switches)
- and of course, backlighting which makes the keys visible in a dark room and more customizable