What does 4E mean in New Balance shoes?

Excuse me, I'm curious to know, what exactly does the notation '4E' signify when it appears on New Balance shoes? Is it related to the sizing, perhaps a specific width measurement? Or does it denote a particular style or technology utilized in the shoe's construction? I'm quite interested in understanding the significance of this designation, as I'm considering purchasing a pair and want to ensure they fit and suit my needs accordingly.