The phrase "mobile platforms" refers to the operating systems or software that allow you to use mobile devices like smartphones and tablets. Full definition
At Another Place we have built a kick ass team of game makers to produce the best free to play Role Playing games on mobile platforms. (anotherplaceproductions.com)
The company will optimize that content for mobile platforms in a way that allows publishers to distinguish their products through design to attract readers and advertisers. (computerworld.com)
The problem thus far has been that most major content producers are not actively targeting mobile platforms with their Flash content. (mashable.com)