When bye week is enabled for a league, each player's worst week is removed from their total points. The player's win/loss record is not affected (wins and losses during the removed bye-week will still be accounted for in the player's overall win/loss record).
Removing a week is a little counter-intuitive. So instead of thinking of it as removing the worst week, instead think of it as keeping the best weeks. The worse your worst week is, the more the bye week helps. For example, imagine two players, player A, and player B, who each earn 12 points every week except one. On the different week, player A only earned 3 points, while player B earned 5 points. Without a bye week, player B would be ahead of player A by two points. But with bye week enabled, player A would instead be tied with player B. This illustrates that a bye week helps the worse your lowest-point week is.
One player suggested he should just skip a week to have a really bad week as his bye week. But this also misunderstands the bye week and would be a bad strategy. For example, let's assume a 4 week season. In each of the 4 weeks, the player gets 12, 10, 6, and 8 points. With the bye week their total is 12+10+8 = 30 (keeping the best scores). If bye week isn't enabled, their total points would be 36 points. If they had decided to skip a week, and happen to skip the week they would have done the worst, their total is still 30 with bye week, and 30 points without a bye week. If they skipped the week that would have been the 2nd lowest week had they picked, their total would be 12+10+6 = 28 points (with or without a bye week). If they really mess up and skip the week they would have done the best they end up with 10+6+8 = 24 points (with or without a bye week). Notice that skipping a week means their best possible score is equal to or lower than had they not skipped a week. Hence the odds are very strong that over a full season intentionally skipping a week will do harm, since its likely that skipped week would not have been the player's worst week (and even if it was, its a wash).
To summarize, the bye week removing the worst week means the player's other, better weeks are being used to determine their total points.