Short answers, pulled from the story.
A lock is a device used for raising and lowering boats, ships and other watercraft between stretches of water at different levels on rivers and canals. Its defining feature is a fixed chamber in which the water level can be varied. A boat enters the chamber, the gates close, and the chamber is filled or drained until the water matches the next level, after which the far gates open and the boat moves on.
The pound lock was pioneered by the Song politician and naval engineer Qiao Weiyue, a high-ranking tax administrator, in 984 in China during the Song dynasty. He installed a pair of sluice-gates two hundred and fifty feet apart on the West River near Huai'an in Jiangsu after grain barges were repeatedly wrecked there.
A flight is a series of separate locks in close proximity, each with its own upper and lower gates and a navigable pound between them. A staircase is only a staircase when successive chambers share a gate, so the upper gate of one lock is also the lower gate of the one above, with no pound in between. Some flights, such as Watford and Foxton, include or consist entirely of staircases.
A caisson lock was a design proposed by Robert Weldon around 1800 for the Somerset Coal Canal, in which a boat was sealed inside an enclosed wooden box that moved up and down through an 80 ft long, 60 ft deep pool of water, wasting almost no water. One was built and demonstrated to the Prince Regent, later George IV, but engineering problems meant the design was never put into use on the Coal Canal.
In 2016 the Kieldrecht Lock in the Port of Antwerp in Belgium took the title of the world's largest lock from the Berendrecht Lock and still holds the title for largest volume. In 2022 the IJmuiden sea lock serving the Port of Amsterdam became the world's largest lock by surface area, measuring 500 m long, 70 m wide, with a usable depth of 18 m.
The miter gate arrangement, the most common type of lock gate, was invented by Leonardo da Vinci sometime around the late 15th century. Miter gates are watertight doors made as a pair of half-gates that seal off the chamber from the upper and lower pounds.
Passing through a lock usually takes between 10 and 20 minutes, depending on the size of the lock and whether the water in the chamber was already at the boat's level when it arrived. Meeting an oncoming boat that has just left the lock at your level sets the lock in your favour and can save about 5 to 10 minutes.