Lidar /scan topic readings

In the ROS basics in 5 days project we are using the /scan topic to get our readings. and it is stated that the minimum angle is -3.14 and the maximum angle is 3.14 so it is a 360 degree lidar and it returns a tuple of size 180 named ranges containing the readings.
I tried to understand where does the readings start but I cannot seem to find an answer.
does index 0 mean forward or backward or right or left??

In my experience, index 0 refers to the back of the robot, and index 89 is the front readings. You can check it by moving the robot to a certain point in the environment and checking the readings. for example, stop the robot close to a wall.

Thanks a lot it worked for me