The expression \( x^2 - 4 \) is a difference of squares, which can be factored using the formula:
\[
a^2 - b^2 = (a - b)(a + b)
\]
In this case, \( a = x \) and \( b = 2 \). Thus, we can factor \( x^2 - 4 \) as follows:
\[
x^2 - 4 = (x - 2)(x + 2)
\]
So, the factored form of \( x^2 - 4 \) is \( (x - 2)(x + 2) \).