What is the difference between an Excel Table and a normal range, and why use named ranges?

An Excel Table — created with Ctrl+T — is a defined object rather than a loose collection of cells, and it changes several behaviours:

• It expands automatically. Add a row and formulas, formatting, PivotTable sources, chart ranges, and data validation all extend with it. This alone removes a whole category of "the report missed the last month" errors.
• Structured references. =SUM(Sales[Revenue]) instead of =SUM(C2:C5000) — readable, and it never points at the wrong range.
• Formulas fill down automatically across the column.
• Built-in filter buttons, banded rows, and a total row with a dropdown of aggregations.
• A header row that stays visible when scrolling, without freezing panes.

Named ranges give a meaningful name to a cell or range. =Revenue-Costs is self-explanatory where =B12-B18 is not, and if a constant is used in fifty formulas, changing it in one named cell updates everything.

Note: Two practical points. Rename tables immediately — Table1 and Table2 defeat the purpose. And be aware that structured references behave differently inside and outside the table, and that some older features and shared workbook functionality do not work with tables, which is occasionally why you would keep a plain range.