Some questions about the max_velocity and max_acc

Hello everyone:
I am new with the Linuxcnc and I intent to control a robot with linuxcnc, the version is axes_joints13 and I have some questions in ini configuration.
1.I am confused with max_velocity and max_acceleration which are listed both in [DISPLAY] and [TRAJ] section in ini file, I don't understand the difference between them and what roles dose each does in the real moving;
2.Just as I am using the axes_joints13 and the controlling object is a robot, it has a separted axes and joint configuration which is [AXES_n] and [JOINT_n] in ini file. I really know the max_velocity and max_acceleration in the [JOINT_n] section which represent the robot joint ,but how I should to set the paremeter of max_acc and max_velocity in the [AXES_n] section? also the max_acceleration and max_velocity in the [DISPLAY] and [TRAJ] section?
Maybe it is very simple In your opinion, but I really a new studier.Thank you everyone

It can be a little confusing, but it can all make sense if you think about it long enough (and maybe have it explained to you once or twice)
The max and min settings in the ini [DISPLAY] section are for setting the limits on the sliders in user display (jog rates, overrides...)
The ones in the [TRAJ] section set the velocity and acceleration limits for combined joint and axis moves. So that say a diagonal move in the XYZ direction can have different limits than a single axis move in just the X direction.

Most likely the most important limits to get right are going to be your Joint(n) limits. They of course are the limits for each individual motor on your machine and should be relatively simple to figure out.

The Axis(n) limits are going to be the limits for movement in Cartesian space (XYZ...) Depending on your kinematics these may be quite different from your Joint limits.

The actual limits of any movement are going to be determined by the slowest piece in the puzzle be it joint, axis or traj. If for exampl you want all of your movements to be the fastest possible, the only ones that are going to matter will be the Joint limits, set all the others high enough so they don't get in the way.

Thank you very much. I think I really understand the concepts.The kinematics module is genserkins,You mean when I set the parameters, I just set accurately in joint_n ,right?
thank you

In a perfect world yes. However I could see the compound movements of multiple joints creating unrealistic velocities and accelerations. That could be a good reason for using appropriate numbers in the other limits.

Thank you very much.I know what you mean. There is other question: I use the same parameteris in the ini file which can control a real robot to run in a normal way in the simulation mode,it has a discontinuous move,the kinematics module is genserkins,I don't know the reason.
Best wishes.