What is "The Log"?

Whenever I try to pull up the play screen for the Sims 3, it shows up with a message saying "There was an error during your startup, go to the Log for more information." What is the Log? How do I get to it? I've been trying to solve this for 5 hours, and I am fairly frusterated, for I would like to actually play the game I have purchased. Please help me soon!