There are several differences between the book and the movie Sense and Sensibility, originally authored by Jane Austen and adapted for film by Emma Thompson, who also stars as Elinor. Naturally, the book includes more detailed dialogue and takes more space describing characters and scenes. It’s a long book! The movie has a limited time in which to portray all of this, so the script has to condense a few things. All in all, it doesn’t lose much of the original storyline.
For one thing, the characters’ ages are adjusted. In the book, Elinor is already considered (by her snobby relatives) an “old maid” at the ripe old age of nineteen, and Marianne is a perfectly marriageable sixteen. Emma Thompson and Kate Winslet are obviously older in the film; their ages are officially nineteen (Marianne) and twenty-seven (Elinor). Colonel Brandon’s dramatic rescue of Marianne from the rainstorm toward the end of the movie doesn’t happen in the book. Instead, Marianne falls ill with a cold in a much more natural way over a few days. Margaret (the youngest sister) and Edward Ferrars (Hugh Grant in the movie) are given more lines and more developed characters all the way through the film. Margaret has very few lines in the book, and Edward has almost none in the beginning of his relationship with Elinor.
Personally, Sense and Sensibility is one of my favorite Jane Austen novels, and I think the film is an amazing rendition of the story, its characters, and the time period. I hope this is helpful!