The idea behind logarithms is that it is possible to take any positive number (other than 1) and, if you raise it to the correct power, get any other positive number. For example, it is possible to raise 12 to some power and get 1/2. Or raise 3 to some power and get 153. The tricky part is finding out wht these exponents are. What power of 12 results in 1/2? And what power of 3 results in 153?
Logarithms are used to express these exponents. For example represents the exponent for 12 that results in 1/2. And represents the exponent for 3 that results in 153.
Now let's look at
Let's look at just the exponent: . This is "the exponent for 4 that results in 5" or "the power of 4 that results in 5". And where do we find ? Answer: As an exponent for 4! Since your expression raises 4 to the power of 4 that results in 5, your expression is simply a 5!