With is a preposition that indicates association, accompaniment, or possession. It is used to connect two or more things together or to describe the manner in which something is done. For example, you can say 'I went to the park with my friends' to indicate that you were accompanied by your friends. 'With' can also be used to express possession, as in 'The book with the red cover is mine.' Additionally, 'with' can be used to describe the way in which an action is performed, such as 'He painted the picture with a brush.' Overall, 'with' is a versatile word that helps to establish relationships and provide additional context in sentences.