Dominant Pole Approximation for loop gain
The numerator and denominator part of the transfer function show where the zeros and poles are respectively placed. The zero locations are determined, by finding the s value in the numerator which would lead to a closed loop response equal to 0. And, the pole locations are determined, by finding the s values in the denominator which would lead to a closed loop response approaching infinite.

In your case, the system has no zeros (numerator has no s). And by inspection you can determine that it has 2 real poles and one complex pole.

Real pole 1: If the first s is set to 0, the numerator becomes zero, hence the transfer function will approach infinite, meaning that you have a pole at the origin \$\omega=0 rad/s\$.

Real pole 2: If the second s is set to -2 , the transfer function will also approach infinite, meaning that you have a pole at the origin \$\omega=2 rad/s\$.

Complex pole: If the last equation is solved for s, it yields \$s= 2\pm i\$, which also make the transfer function approach infinite..

Just to to have a graphical representation, you can see the bode plot of your transfer function in the following diagram (\$K=1\$):