What is an included IF function in which the action to be taken for the true or false case includes yet another IF function?

You insert the second IF function into the first one, creating what is called a nested If. Another IF can be put in the True or False part of an existing IF function. In as situation where there is a need for another IF when the first condition is true, the structure could then be something like this:

=IF(condition, IF(condition, true, false), false))

Note there are two brackets at the end, closing the two IF functions.