The Q text is a theoretical ‘source’ document of Matthew, Mark, and Luke. In analyzing these three text scholars (mainly of a more liberal bent) see whole passages (down to every sylables) that are exactly the same between two or more of these gospel account. So these people assume that a larger more complete account of Jesus’s life was written prior to Matthew, Mark and Luke that served as their source. Off hand it is not to heretical of an idea since these three ‘synoptic’ gospels share many traits. For instance Luke directly says that he did a lot of research for his account. But some will use this to weaken the claims of the bible by saying that it proves that these did not come about from direct eye witness account. I am sure if you look on http://www.equip.org or other links that more information could be found.