1"Older sister" — the polite, everyday way to refer to or address one's elder sister within the family.
私のお姉さんは看護師をしています。
My older sister works as a nurse.
お姉さん、ちょっと手伝ってくれない？
Sis, could you help me for a bit?
弟はいつもお姉さんの後をついて回る。
My little brother always tags along after his older sister.
2A vocative term used to call out to or refer to a young woman one doesn't personally know, similar to "miss."
すみません、お姉さん、この道でいいですか？
Excuse me, miss, is this the right way?
駅で「お姉さん、ハンカチ落としましたよ」と声をかけられた。
At the station, someone called out to her, "Miss, you dropped your handkerchief."
小さな子が公園で知らないお姉さんに手を振っていた。
A small child was waving at a young woman they didn't know, in the park.
3Used to address or refer to a young female worker in a restaurant, bar, etc., such as a waitress. Sometimes written お姐さん.
お姉さん、お会計お願いします。
Miss, could I get the check, please?
居酒屋のお姉さんが笑顔でメニューを持ってきた。
The waitress at the izakaya brought the menu with a smile.
「お姉さん、生ビールもう一つ！」と客が呼んだ。
A customer called out, "Miss, another draft beer, please!"
4A respectful term used within geisha circles and similar traditional trades to address a senior woman.
新人の芸者はお姉さんから礼儀作法を教わる。
The new geisha learns manners and etiquette from her senior.
お姉さんに言われた通りに着物を着付けた。
She put on the kimono exactly as her senior had told her.
5Refers generally to a girl or young woman older than the speaker, without implying any family relationship.
近所のお姉さんによく遊んでもらった。
I often got to play with the older girl who lived nearby.
あのお姉さんは高校生に見える。
That girl looks like she's in high school.