The following figure shows the graph of \(y = f\left( x \right) = {x^2}\):
Using this graph, can we plot the graph of the function \(g\left( x \right) ={\left( {x  2} \right)^2}\)?
We make some example observations:

The zero of the original function f is at \(x= 0\); the zero of the function g will be at \(x = 2\). Thus, the zero will rightshift by 2 units.

The function f attains the value of 1 for the values \(x = \pm 1\); the function g will attain the same value of 1 for \(x = 1,3\).Once again, relative to the original graph, these values have rightshifted by 2 units.
Clearly, any value which the function f attains at an input value of \(x ={x_0}\) will be attained by g at an input value of \(x = {x_0} + 2\). In other words, if \(\left( {{x_0},{y_0}} \right)\) is a point on the graph of f, then \(\left( {{x_0} +2,{y_0}} \right)\) will be a point on the graph of g. This indicates that the whole graph will get right shifted by 2 units:
Similarly, the following figure shows how the graph of the function \(h\left( x\right) = {\left( {x + 2} \right)^2}\) can be obtained from the graph of f by leftshifting it by 2 units:
In general, the graph of \(y = f\left( {x + k} \right)\) can be obtained by horizontally shifting the graph of \(y =f\left( x \right)\) by \(\left k \right\)units . The direction of the shift will depend upon the sign of k. If k is positive, the shift will be leftward, else it will be rightward.
As another example, consider the following figure:
The dotted curve corresponds to the graph of some arbitrary function, \(y = f\left(x \right)\). The solid curve represents \(y= f\left( {x + 3} \right)\). Note how each point on the original curve can be leftshifted by 3 units to obtain the new curve.