What is the purpose of the colspan attribute in HTML?

The colspan attribute in HTML is specifically designed to indicate how many columns a single cell should span within a table. When you apply the colspan attribute to a (table data) or (table header) element, you can merge that cell across multiple columns. This feature is particularly useful when you want to create complex table layouts, allowing for a cell to occupy a wider horizontal space than a standard single cell.

For instance, if a table has 5 columns and you set colspan="3" for a cell, that cell will extend across 3 of those columns, effectively allowing you to control the structure of your table and arrange data more effectively. This can enhance readability and help in showcasing related information cohesively within the confines of the table. The other options address different aspects of table design; however, only the colspan attribute directly relates to spanning across multiple columns.