Click on the image at the left to download and play the PhET Maze Game from the University of Colorado at Boulder. If you think you understand the concept of acceleration, try the Acceleration setting on the game for Level 2. See the red circles in the image below.
Just to be fair: you can watch me play the Maze Game in the video below.
After manipulating the acceleration of the ball in the Maze Game, it should be fairly clear that you, like most everybody else on the planet, have a difficult time with the concept of acceleration.
Hopefully, you can get a clearer understanding of acceleration by reading this section of the textbook.