The ROS navigation stack is the most powerful software package that allows mobile robots to move from one place to another safely. The goal of the navigation stack is to produce a safe path, in other words, a collision-free path for the robot to execute by processing the data from sensors and the environment map. One of the great functionalities of the navigation stack is obstacle avoidance. We can easily view this feature by adding an object in front of the moving robot in Gazebo.