How did it happen in the movie?
This scene opens with Gollum returning to Frodo and Sam, bringing with him two rabbits that- much to Gollum’s dismay- are stewed by Sam. As Sam tends to the stew, he has a rather argumentative discussion with Gollum about food; Gollum believes fish should be eaten raw, and that “taters” are nasty while Sam is the complete reverse. While they argue, Frodo is rummaging around in his pack, but stops suddenly hearing a strange noise in the background, and slips away quietly to discover the source of the noise. He wanders in the forest for a moment until, coming to a bluff, he lies down on his stomach and looks out. There, a strange sight met his eyes; a substantial army of Haradrim warriors was on the march down below. As he watches the army move, Sam and Gollum come up behind him. Upon being asked who the men were, Gollum replies that they are “Wicked men. Servants of Sauron. They are called to Mordor. The dark one’s gathering all armies to him. It won’t be long now, he will soon be ready.” Sam inquires as to what he will be ready for, so Gollum answers “To make his war. The last war that will cover all the world in shadow.” Frodo’s face appears sickened as he gets up to move away, however Sam holds him back as amazed, he points out an Oliphant that has appeared with the Haradrim.
At that point, Frodo and Sam hear a strange cry, very like to the call of a bird, and a rain of arrows begins wreaking havoc upon the men below; we also see short glimpses of cloaked and hooded figures shooting from the bushes. One dead body falls off of an Oliphant, and lands very near to the place where the hobbits are hidden. Seeing this, Frodo realizes that they have stayed too long, so he turns to depart, but runs straight into one of the cloaked men. He struggles wildly but is unable to free himself; even Sam’s efforts are in vain as they are both easily overcome. Here, Faramir makes his appearance, though he is not called by name. He speaks to the hobbits sternly and appears to suspect the hobbits of being in league with the enemy. Walking over, he looks down at the body of the fallen warrior, and seems to become a bit more thoughtful as he wonders aloud whether the man was truly evil at heart. Afterwards, he orders the hobbit’s hands bound, leading them away.

How did it happen in the book:
This chapter begins a bit more slowly then the movie version, as the first few pages describe about two days of journeying through Ithilien. The hobbits finally stop to rest in a small thicket of bay trees not too far away from a lake. As Gollum sneaks off on his own Sam asks him to bring back something fit for a hobbit to eat, and surprisingly enough, Gollum replies agreeably, returning after a time with two small rabbits. Sam eagerly begins to dress them and prepare a stew, keeping Gollum busy by sending him to fetch water. Once Gollum realizes what Sam plans to do with the rabbits, he raises a complaint to which Sam replies by telling him to keep out of sight if he didn’t wish to see it. Grumpily, Gollum moves on, and refuses to help Sam find herbs for the stew. The two get into a brief argument about potatoes as Sam claims he can make excellent fish and chips and Gollum rudely denies this, arguing that raw fish is much better.
Once the stew is finished, the two hobbits eat their meal. While Sam washes up afterwards, he suddenly realizes that he has neglected to douse the fire and it has now started smoking- betraying their presence to anyone who may be about. Quickly he puts out the flames, only to realize that they have been discovered. A strange cry is heard much like the call of one mimicking a bird, and nervously the two hobbits creep into the ferns to hide. Shortly afterwards, they are discovered by Faramir, and three of his rangers. Faramir questions Frodo, but does not have the time to question very extensively. An army of Haradrim was passing nearby, and he intended his company to ambush them. So leaving Frodo and Sam to be guarded by two of his men: Mablung and Damrod, Faramir took his company after the men of Harad. After talking with their guards for a short time, Frodo and Sam rest, and await Faramir’s return.

Changes:
-In the book, Sam leaves a fire burning, accidentally alerting Faramir to their presence. They are caught in some nearby ferns. In the movie, this was altered so that Frodo and Sam are looking over a ledge at the Haradrim right before they are caught.
– The scene with Faramir and the dead Haradrim was actually taken from later in the chapter; Sam glimpses the dead body of a Harad warrior and wonders silently to himself about the man and what he was like.
-In the books, Faramir was somewhat more courteous to the hobbits, leaving them under guard rather then binding their hands and leading them away as captives. He also spends more time in discussion with Frodo before leaving.