VLOOKUP

This function is good for looking up information in big tables without having to scroll all over the place.
Say, there is huge spreadsheet containing data about items and their prices, size, package, whatever. The item is listed in the first column, all other information in the columns to the right. A big table with lots of data. Somewhere else the spreadsheet shows a summary of special items in this database, e.g. only selected items and their available stock. The summary lists a few items, with VLOOKUP the number of pieces in stock is automatically written into the cell.

Another idea could be to lookup share prices in a table and, by adding another couple of calculations to that formula, calculate the profitability - or list only those share prices you want to see from a huge database (for those who don't want to have the internet calculate their funds).