Accounts run on master tables: a price list, a GST rate list, a salary master. A lookup fetches one value from that table for you, so you never retype a price by hand.

VLOOKUP(what to find, table, column number, FALSE) searches down the first column of the table. When it finds the value, it moves across that row and returns the cell in the column number you gave. Column 1 is the table's first column, column 2 the next, and so on.

The trap: always end with FALSE for an exact match. If you leave it out, VLOOKUP guesses (approximate match) and can quietly return the wrong row. If the code isn't in the table at all, you get #N/A.