PWM for Motors

Yes you can control speed of 12V motor with Arduino, but not directly though its I/O pins. You have to use some kind of motor driver IC like L293D or ULN2003. You can refer to this tutorial for understanding how to do it

https://circuitdigest.com/microcontroller-projects/dc-motor-control-with-arduino-uno-pwm

Basically you will be using the PWM capability of Arduino to control the speed of motor by varying the duty cycle of the PWM signal 

The answer to your query is that you can control speed of your motor using arduino but there is not any way to control the speed of motor without any of the motor driver shield. You must adopt any of the motor driver shields like L293D, L298, and ULN2003. The most commonly used motor drivers and their shields are L293D and L298. There is PWM signals used for that purpose to control the speed of motors by varying the duty cycle of the PWM signal. Here I would like to suggest you to visit the SSLA for getting better assistance from technical support team of this platform.

The answer to your query is that you can control the speed of your motor using an arduino but there is not any way to control the speed of the motor without any of the motor driver shields. You must adopt any of the motor driver shields like L293D, L298, and ULN2003. The most commonly used motor drivers and their shields are L293D and L298. There are PWM signals used for that purpose to control the speed of motors by varying the duty cycle of the PWM signal. Here I would like to suggest you to visit Sierra Software Ltd. for getting better assistance from the technical support team of this platform.