Throughout reading some online reference and videos, I found that servo motor is basically a DC motor, along with some other special purpose components that make a DC motor a servo. It consists of a small DC motor, a potentiometer, gear arrangement and an intelligent circuitry.
For the connection, most of servos have three circuits, which can be connected with the arduino and controlled by the coding. In three of them, two connects with the 5V because normally it is the power working condition of the servos, whereas another circuit is responsible to communicate with arduino and get the data.
The intelligent circuitry along with the potentiometer makes the servo to rotate according to our coding. Also, I found a small DC motor will rotate with high speed but the torque generated by its rotation will not be enough to move even a light load. The gear mechanism will take high input speed of the motor (fast) and at the output, we will get an output speed which is slower than original input speed but more practical and widely applicable.