A narrow gate into the main draw
Before the familiar main draw of a tournament begins, a much larger qualifying field plays a compressed knockout, often three rounds, to fill a small number of remaining places. Because the field is large and the rounds are few, qualifying is statistically less forgiving than the main draw it feeds: a single off day removes a player entirely, with none of the ranking-point cushion that a first-round loss in the main event still provides. It is, in a small way, the sport's purest form of pressure, since almost nothing beyond the match in front of a player matters at that moment.
Where most matches are actually played
Beneath the tournaments that receive broadcast attention sits the challenger tour, a lower tier of events offering smaller prize money and fewer ranking points but running in far greater number across far more locations. The overwhelming majority of professional matches in any given week are played at this level rather than at the visible top of the sport, and it functions as both a proving ground for rising players and a lifeline for established ones working back from injury or a ranking slump.
A different kind of economics
Because challenger prize money is modest, success at this level is measured mostly in ranking points banked toward eventual direct entry into bigger events, set against the very real costs of travel, coaching and accommodation involved in playing week after week. Players at this stage are essentially investing their own money in a points total that may or may not translate into sustainable earnings later, which makes the challenger tour as much a financial gamble as a sporting one.