Knew is the past form of 'know'. It means that you had knowledge or information about something in the past.
I knew the answer to the question.
She knew him from school last year.
Knew can mean you met or have experience with someone in the past. It shows you were familiar with that person.
He knew my friend from the park.
They knew each other very well last year.
Using 'knew' can mean you understood or realized something in the past, showing you had knowledge before now.
I knew the plan was not good.
She knew the truth after the story.
'Knew' shows you were aware or had certain facts in your mind at a past time.
She knew about the meeting yesterday.
They knew the rules before the game.
Sometimes 'knew' means to have felt or gone through feelings or events in the past.
He knew sadness after the loss.
They knew joy during the festival.
'Knew' can mean having sexual relations, especially in old texts or the Bible. It is a formal and not common modern use.
He knew her before they married.
The phrase 'to know someone' means a close relationship.
