A function is said to be increasing when, as the $x\text{-}$values increase, the values of $f(x)$ also increase. On the other hand, the function is considered decreasing when, as $x$ increases, $f(x)$ decreases. An increasing interval is an interval of the independent variable where the function is increasing. A decreasing interval is an interval of the independent variable when the function is decreasing. Any points where a function has a maximum or a minimum are not included in either interval. The previous applet shows a function that contains two increasing intervals and one decreasing interval. Each can be described in terms of the $x\text{-}$values.
Although the entire graph cannot be seen, it is reasonable to assume that it continues in the same manner. In that case, for all $x\text{-}$values less than $x=\text{-}2,$ $f$ will be increasing. For all $x$-values greater than $x=0,$ $f$ will also be increasing.
The point where a function switches between decreasing and increasing is known as a turning point.