Which of the following best describes a 'header' in a spreadsheet?

A header in a spreadsheet is best described as a title or label for a row or column. Headers provide context and clarity to the data presented in the spreadsheet, helping users understand what each row or column represents. By labeling them appropriately, headers facilitate easier navigation and analysis of the data. For example, if a column contains sales figures, the header might be labeled "Sales" to clearly indicate the type of information found in that column.

The other options do not accurately define a header. Information about the file size relates to the properties of the spreadsheet file itself, rather than the content within it. A section where data is stored could refer to any part of the spreadsheet but does not specifically capture the function of a header. A command button in the toolbar pertains to the software interface and is unrelated to the concept of headers that organize data within the spreadsheet.