Remapping between nodes

edit

Basically, remap is a feature to rename topics, node names and some special keys of ROS env. You can see in this page what you can remap, like a node name (__node), namespace (__ns), log file (__log), etc.

Example: I've a node that publishes Twist messages in a topic called turtlebot_vel, but my robot listens to cmd_vel

You can remap using rosrun command, like this:

rosrun my_pkg my_node.py turtlebot_vel:=cmd_vel

Or inside a launch file (ref):

<launch>
    <node pkg="my_pkg" type="my_node.py" name="my_node">
        <remap from="turtlebot_vel" to="cmd_vel"/>
    </node>
</launch>