Normally a good novel (especially mystery or thriller) is often said to be “tightly plotted”. What does it mean? In contrast what does “loosely plotted” mean?

Please give example in your explanation.

I have read somewhere that John Grisham is a master plotter and all (or most, if not all) of his novels are tightly plotted. What does it mean?
- Ray Mystery

i have already read da vinci code, close to all books of agatha christie, jeffrey archer and john grisham,harry potter, lord of d rings
- Riti

First off, I’m 19 and I’m a guy. Most books I read pertain to sports, historical fiction, or just some classic literature. Some of my favorites include: “Walk In the Woods” by Bill Bryson, “Bleachers” by John Grisham, and Tony Dungy’s book. I just want some thoughts from you guys on what you think would be a good book for me to read. It can be one of your favorites or not, I don’t care.
- Chandler C