So the graph shown is for the 1st derivative of f(x).

The function f(x) increasing if the 1st derivative is positive.

So, that is in the intervals (-2,-1) and (2, +infinity)

Or, from just after x = -2 to just before x = -1, and then, from just after x = 2 to positive infinity.

The function f(x) is decreasing if the 1st derivative is negative.

So that is from negative infinity to just before x = -2, then from just after x = -1 to just before x = 2.

f(x) has horizontal tangent lines where the 1st derivative is zero.

So those are at x = -2, x = -1 and x = 2.

f(x) has an inflection point where its 1st derivative is at maximum or minimum.

So those are at x = -1.5 and x = 1, if my eyes can see clearly.