Check out this video about using VLOOKUP. For example, look up an employee's last name by her employee number, or find her phone number by looking up her last name (just like a telephone book). Use this function when you need to find things in a table or a range by row. Use this function when you need to look in a single row or column and find a value from the same position in a second row or column.
Here's a video about using the IF function. Use this function to return one value if a condition is true and another value if it's false. Use this function to add the values in cells. Here are the 10 functions that people read about most.