Young Jacob may be Bella's favorite non-vampire friend. He's a Quileute Indian and lives on La Push reservation, not far from Forks. Upon first meeting, Bella is genuinely charmed and impressed by Jacob in many ways – he's a breath of fresh air compared to how clingy and suffocating Bella considers her Forks friends. Jacob and Bella's initial connection is that Jacob's dad, Billy, is friends with Charlie, and Bella's truck used to belong to Billy. Bella goes on to learn that Jacob is really into rebuilding and fixing cars.
We get the impression fairly quickly that Jacob is similar to Bella in many ways. He's very "normal," but there's something extra about him that makes him special. He's interesting and genuine. Bella notes that Jacob seems to have a crush on her, but Bella doesn't seem to be viewing Jacob in a completely platonic (non-romantic) way, either.
Let's take this one step further. Jacob seems like safe boyfriend material, the kind of guy Charlie would be OK with Bella dating. Overall, part of Jacob's role in the book is as a contrast to Edward, because both are potential love interests for Bella. Let's examine some of the ways they're different.
For starters, Edward is older than Bella (about 90 years older, in fact) and has a lot of life experience. Jacob, however, is a bit younger than Bella – Edward even calls him a "child." Edward is mysterious and challenging for Bella to understand, whereas Jacob is easy to read and even easy for Bella to manipulate. Edward represents danger and excitement, while Jacob is kind of like a safe boy-next-door type (and the son of Charlie's friend). Edward is graceful and sweeps Bella off her feet when dancing; Jacob is endearingly awkward at prom. By the Epilogue when Bella says, "I was shocked to notice that Jacob didn't have to look up [to glance at Edward]. He must have grown half a foot since the first time I'd seen him" (Epilogue.59), we imagine that Stephenie Meyer is going to have a bit of competition between Edward and Jacob in the sequel.