A view bar is a screen element of application that appears along the left edge of the window.
The View Bar displays icons of the most commonly used views (Gantt Chart, Resource Sheet, and so on).
View: The combination of one or more views and if applicable, a table and a filter.
Use views to work with information in a variety of formats. There are three types of views: Charts or graphs, Sheets, and Forms.
You can click an icon to display the view.
The View Bar provides a convenient means of changing views by just clicking the icons that appear on the View Bar.
By selecting the View Bar option from the Window menu, the view bar can be hidden or displayed according to the user needs.
Some of the custom views that were saved with the project plan can appear in the view bar like in the picture below: