It does not matter if you know everything or know nothing. Take 3 minutes to do it then have fun following it for the next 3 weeks.
Bracketology is the process of predicting the field of the NCAA Basketball Tournament, named as such because it is commonly used to fill in tournament brackets for the postseason. It incorporates some method of predicting what the NCAA Selection Committee will use as its Ratings Percentage Index in order to determine at-large (non-conference winning) teams to complete the field of 65 teams, and, to seed the field by ranking all teams from first through sixty-fifth. ESPN's Joe Lunardi is the inventor of the term "bracketology", starting first as the owner and editor of the Blue Ribbon College Basketball Yearbook and ending up with a gig as the resident bracketologist on ESPN. 
Using the NCAA basketball tournament selection process, the RPI, and the seeding and balancing process, a "bracketologist" places teams in the tournament in the various regions (East, West, Midwest, and South). Some bracketologists go as far as placing teams in which "pods" they will play in the first and second rounds. Generally, the lists also show the last four teams in and the first four teams out. However, these brackets change daily as conference tournaments continue and teams automatically qualify for the tournament.
A bracketologist's credibility is judged on how many teams he predicts correctly being in the tournament and the average difference between the bracketologist's projected seed and the actual seed assigned by the NCAA Selection Committee. The difference between projected matchups and the differences between the "pods" selected in the first and second rounds are less important.
There are many motivations for a bracketologist. For Lunardi, he was already gathering statistics and information in his role as Sports Information Director for Saint Joseph's University and editor of the Blue Ribbon Yearbook on men's college basketball, so it was not much more effort to predict the brackets. Others are motivated at perceived flaws in other bracketologist's predictions, such as putting too much (or too little) emphasis in the RPI, favoring lesser or major conferences, or failing to consider factors such as performance in the last few games.