Tools vs. Platforms

Hello to all in the Forum! I have been an UI/UX designer for two years in Germany. I am now based in London studying Computing and Social Media.

For my own research practice I wanted to start a discussion on the conceptual models, current ideas regarding the design of 'platforms' vs. 'tools' for users or for social media.

Are these concepts changing? Think about this also in terms of desktop computers, or mobile devices..