Jill is probably most people’s first choice as their character in Resident Evil. Her easier mission, larger item carrying ability and more powerful weapon selections make the game very good for Resident Evil beginners. Jill seems to be a little unaware to things going on around her at times during Resident Evil, even though she is supposed to be intelligent, well according to the info from Capcom anyway.
Arguments are caused about her past. From her return in Resident Evil 3, we learn she is ex-delta force (something which makes no sense by her age-yet again this is Capcom's info for you), but according to the book, for which some people cling to too much like a holy Resident Evil bible or something, it seems Jill used to be a thief because of her father, the job that made her "the master of lock picking."
How Jill ended up as a STARS member is still unknown. If we were to go and follow the SD Perry novels path, it would seem her jailbird father told he to get out of the family business and join the other side of the law. Either way, and yet again against Capcom's info where she has quit in RE3 due the the problems of being a STARS member, it seems she is proud of her accomplishments and being part of the STARS unit regardless of the problems happening within Resident Evil.
Jill's weapon assortment is powerful. Bazooka (with 3 types of ammo), Shotgun, Magnum, Beretta, and of course the standard combat knife. Details on each of the weapons that Jill uses can be found in the Resident Evil weapons section here.
Jill holds more items than Chris (8 instead of Chris' 6) and this makes the game easier as you'll have to do less item juggling and combining. She also has a lockpick which gives you access to doors and draws that Chris will have to use keys with. Barry will also give you the occasional piece of ammo, but unlike Chris with Rebecca, you will never get the chance to play as him.
Jill has also returned in later games. She is the main character of Resident Evil 3, and is also mentioned various times throughout the later sequels in files and such other details within the following games.
Jill, back from the first Resident Evil, has seen a lot of changes happen in her life since the "mansion incident" and although it seems she has quit the S.T.A.R.S. due to the chief of police ignoring the S.T.A.R.S. warnings of the dangers they faced in the mansion, she does continue to use her taskforce authority (and claim to still belong to the S.T.A.R.S. at the same time). The corruption which existed with Chief Irons at the Raccoon Police meant that their warnings could have stopped some of the problems which happened, and finally lead to the outbreak in Raccoon. However it is too late and Jill is left to try to escape the hell that has been created.
Jill has become a more human character in Resident Evil 3 that she was when she appeared in the first game. Give this down to a new voice actor and the various character development scenes which have gone on since the previous game, Resident Evil 2. She will bump into many characters, both bad and/or good, throughout exploring what is left of Raccoon City.
Because Jill is really the only character in Resident Evil 3 (besides a small stint as Carlos) she has just about all the weapons you use in the game. Everything from handguns to Rocket Launchers, Mine Throwers to Grenade Launchers, Daggers to Rifles. Each has their own use within the game as you would expect.