Explain the differences between one-way data flow and two-way data binding?

In one-way data flow the view(UI) part of application does not updates automatically when data Model is change we need to write some custom code to make it updated every time a data model is changed.

In Vue js v-bind is used for one-way data flow or binding.

In two-way data binding the view(UI) part of application automatically updates when data Model is changed.
In Vue.js v-model directive is used for two way data binding.