What is a workbook in Excel?

A workbook in Excel refers to a set of spreadsheets contained within a single file. This is an essential feature of Excel, as it allows users to organize and manage different sets of data in an efficient manner. Each spreadsheet within a workbook is called a worksheet, and users can switch between these worksheets to analyze or input data without the need to create separate files for each sheet. This structure facilitates easier access to related data, promotes better organization, and enhances data analysis capabilities.

The other options describe different concepts within Excel but do not accurately define what a workbook is. A database of values pertains to data storage and organization but doesn't encapsulate the idea of multiple worksheets. A type of formula used refers to specific calculations made within spreadsheets, while a summary of data analysis describes the results of data processing rather than the structural grouping of spreadsheets within a single file.