Few is less than you want so you are unhappy.
A few is more so you are happy.
- She has few friends.
(She doesn’t have many friends. She is unhappy.) - Few people bought tickets, so the concert was cancelled.
- She has a few friends.
(She has friends. She is happy.) - We have finished everything sooner than expected, so we can leave a few hours earlier.
Little and a little are used in a similar way.