*We use at:
to refer to a position or location which we see as a point:
I was sitting at my desk.
to talk about locations at companies, workplaces when we see them as a place of activity:
How many people are working at Microsoft?
to refer to activities which involve a group of people:
Were you at Lisa’s party? (also at the cinema, at the theatre)
She always did well at school.
to refer to an address:
They once lived at number 12 South George’s Street.
to talk about public places where we get treatments, such as a
hairdresser’s or doctor’s surgery:
I can’t meet at four. I’ll be at the hairdresser’s until five.
to refer to most shops:
Look what I bought at the butcher’s today.
*We use in:
to talk about locations within a larger area:
I know my book is somewhere in this room. Can anyone see it?
to talk about workplaces when we see them as a physical location:
She works in an open-plan office. (but we use on when we talk about
a farm: I’ve always wanted to work on a farm.)
He found it difficult to concentrate in class.