Browse the combination catalogue
Every suit holding worth thinking about, with the best line's odds beside it. Narrow by how many cards the two hands hold between them, by how many times the line has to change hands, or by how often it brings the target home.
What one row is
A row is a holding and a target: these cards, this many tricks. The same cards played for a different number of tricks is a different problem with its own best line, so it gets its own row. That's why a holding you recognise may appear here more than once. Holdings of five to eleven cards between the two hands are covered, but a holding only gets a row if the play is worth thinking about. If the obvious card is already right, there's nothing to teach and the holding is left out.
Reading the columns
Best line makes it is the share of layouts on which the best line guarantees the target. The defenders are assumed to see all four hands and to play best defence (the card that hurts you most, even if a book would play something else). So a line only counts where it works against any defence at all. These numbers are lower than the ones you get by assuming honest opponents, but you can safely bet a contract on them. A plain finesse is fifty per cent, so compare the rest against that.
Entries at worst is the most times the line can need to change hands, counted over every way the missing cards can lie. We use the worst case rather than what the line needs on the deal shown on its own page, because if you can't afford a line when the cards lie badly, you can't play it. Filter to none to answer "I have no way back to dummy, so what can I still play for?" A book can't easily tell you that.
Why the lengths are so uneven
The counts beside the card chips are worth a look before you pick one. Seven- and eight-card holdings carry the most, and carry more rows than there are holdings, because two posable targets on one holding is normal at those lengths. You can play for the extra trick or settle for the safe one, and the two need different cards. At the other end, eleven cards between the hands gives almost nothing: with only two cards missing there is rarely a decision to get wrong. Short holdings are thin for the opposite reason. There are too few cards to give you a choice at all.