Some motors have built-in hall-effect sensors that can detect the orientation of the rotor. Controllers for this type of motor require sensor inputs to read these hall sensors.
Other 'sensorless' motor controllers sense the back EMF in the motor coils themselves to detect the rotor position. Most ESC (Electronic Speed Controls) for brushless RC motors use this technique.
Many BLDC motors have integral controllers. Computer fans are one example. These may or may not have PWM inputs or tachometer outputs. If speed control is one of your goals, be sure that you understand the capabilites of the controller.
Brushless motors designed for autonomous and remote control aircraft and vehicles typically require a separate controller. These are typically of the sensorless type and use standard servo type pulsed signals for speed control.
ESCs for brushless motors are rated by amps. Select an ESC rated for at least as many amps as your motor. If you will be driving the motor hard, a 10-20% safety factor in the ESC rating is a good idea.