Vlookup (and Hlookup)
Vlookup (Vertical Lookup) and Hlookup (Horizontal Lookup) are very useful functions. They let you find things in a table or a range (group of cells). For example, look up a price of an film by its name, or what grade a piece of work earns based on its mark, or to find an employee name based on their employee ID. Watch the videos to see how this works.
Hlookup does exactly the same thing for data laid out the other way round. These are some of my most used functions, and work really well with drop down validation too. They make a great alternative to complex nested if statements.