In this post you can understand what is Workbooks and Worksheets in excel. The Work you do in excel is performed and saved in a file, such excel file is called as workbook. You can open as many excel files you need, and each one appears in different window. Excel workbooks/ files are saved with .xlsx file extension.
Excel file or workbook contains one or more worksheets, and worksheet is made up of rows and columns and individual cells. Each cell can contain a value, a formula or text.
User can access the worksheet in a workbook by clicking the tab at the bottom of the workbook window. In addition a workbook can store chart sheets; a chart sheet displays a single chart and is also accessible by clicking a tab. Within the worksheet. we can also save the charts, graphs, images, diagrams etc.