bro a stage is a race. every day is a stage. it's a huge deal to win a race any time of year. it's even huger to win a race within the greatest of a cycling races . remember winning stages doesn't win you the tour -best overall time does. which is why it doesn't make sense for lance to chase sprint finishes..time bonus sprints maybe....but everyone who finishes in the pack gets virtually the same time.
time trial is a stage where the race is against the clock ie there is no head to head racing. indidividual time trials , like yesterday, each rider rides the course alone, without the benefit of drafting from his team or other riders. it really is the measure of individual strength and for lance or any super strong rider who wants to win the whole she-bang the individual time trials are a great opportunity to put insurrmountable time on other contenders who can't benefit from help from their team.
there are also team time trials where each team rides as a unit and everyone gets the same time. but again it's a race against the clock and they're not mixing it up head to head on those days.