Ros2 node

1. Each node responsible for a single modular purpose
2. Each node can send and receive data from other nodes via topics, service, actions, or parameters
3. a single executable can contain one or more nodes.

Basic Commands

# =================================================
# Node
# =================================================
# launch an executable from a package
ros2 run <package_name> <executable_name>

# list all nodes' name
ros2 node list

# reassign default node properties, like node name, topic names
ros2 run turtlesim turtlesim_node --ros-args --remap __node:=my_turtle

# access more information(publisher, subscriber, service, action) about node
ros2 node info <node_name>