Half Life is a first person shooter that follows a theoretical physicist in the year 2000 in New Mexico. There are some experimental things going on with Gordon Freeman, the games main character, and in the meantime a rift between real world and another, Xen and that is where the fun begins.
Besides the first two, full length games, Valve released two shorter games call Half Life 2: Episode One and Half Life 2: Episode Two. There was supposed to be a third episode to the series released around Christmas of 2007, but that was not the case as fans have seen. So fans have been left waiting for a game, but they might get something else to enjoy.
Back in 2013, Gabe Newell did announce that there was a story he put together for a movie that follows Half Life video games, or one that follows a similar game called Portal. Since that announcement there has not been any other information regarding it, so fans, again are left waiting.