An acceleration of +2 m/s2 means that the velocity of the object is increasing by 2 meters per second every second in the positive direction. For example, if a car is traveling at 30 m/s and accelerates at +2 m/s2, then after one second, the car will be traveling at 32 m/s, and after two seconds, it will be traveling at 34 m/s.
On the other hand, an acceleration of -2 m/s2 means that the velocity of the object is decreasing by 2 meters per second every second in the negative direction. For instance, if a car is traveling at 30 m/s and decelerates at -2 m/s2, then after one second, the car will be traveling at 28 m/s, and after two seconds, it will be traveling at 26 m/s. This is also known as a negative acceleration or deceleration.