Single-Entry is a contest in which only a single entry is allowed per owner. In fantasy football, that means that you are only able to submit one lineup of players. This term is used in daily fantasy sports (DFS) competitions where new lineups can be chosen and submitted every week.
Other than the obvious, that you only get one entry instead of multiple, single-entry tournaments are a far different experience than multiple-entry ones. For starters, the stakes are higher, with the restriction on submissions each individual player's performance is worth more. One bad performance from a player can tank your whole submission.
Single-entry tournaments are ones that appeal to the more casual players. It eliminates the players that submit 10 lineups, taking into account the price gap that may exist. If you have the money or budget, you could submit as many lineups as you wanted, making it unfair to those who can't, the single-entry tournament stops this from happening.
Anyone can get lucky and win money in a single-entry tournament. If you were only planning on submitting one entry anyways, join a single-entry tournament, as your chances of winning will be higher!
With a single-entry tournament, a player must take into account that they must outperform the average person, not match them. People tend to get conservative with their picks, selecting low upside, but talented players. In doing so, the amount of people who take superstars increases and the ownership of lesser-known players decreases.
If you want to win big money in such tournaments, that type of strategy is not a good idea. Instead, going against the grain is your best bet. It is a riskier play, but selecting high upside but low valued players can set you apart from the majority of participants.