The 'Fireside Hangout' held by Obama will be the second on he does following a tradition he began last year by hosting a Google+ visual conference call after his State of The Union address.
During the Hangout, the president will answer questions from select participants in a conversation that will be streamed live. The rest of the world can submit their questions via video or comment in the White House's YouTube channel before 11:59 p.m. ET on Feb. 13 to be considered.
Google put together a promotional video for the Hangout were they give some examples of the type of questions that can and will be asked during the conversation with Obama.
For ideas on what to expect/ask you can check out Obama's hangout from 2012.