Refers to one's own older sister when speaking about her to others, or can be used to address an older sister-like figure. In formal or polite contexts, お姉さん (おねえさん) is often used instead.
My older sister lives in Tokyo.
My older sister is very good at cooking.
I have an older sister who is three years older than me.
She's often told that she resembles her older sister.
As the older sister, I look after my little brother.