When working with KnockoutJS, the with binding allows you to change the current binding context. So if you have a nested data structure, instead of having to binding to properties such as subViewModel.property1 and subViewModel.property2, you can put them inside a with binding and then refer to them directly as property1 and property2, respectively.
This is quite useful in keeping your views from getting too cluttered when your viewmodel structure gets large. However, if you jump down more than one level in a single the with binding, it’s not immediately apparent what the $parent context will refer to.