what is node in selenium grid code example

Example 1: selenium grid configuration

java -jar selenium-server-standalone-2.53.1.jar -role hub -hubConfig hubconfig.json

Example 2: what is node in selenium grid

What is a node in Selenium Grid?
Node is the machine which is attached to the hub.
There can be multiple (preferably) nodes in Selenium Grid.
Selenium Grid uses a hub-node concept where 
you only run the test on a single machine
called a hub, but the execution will be done
by different machines called nodes. 

RemoteWebDriver driver=new RemoteWebDriver (new URL(hubIP), capability);

Example 3: selenium grid configuration

{
	  "port": 4444,
	  "newSessionWaitTimeout": -1,
	  "servlets" : [],
	  "withoutServlets": [],
	  "custom": {},
	  "capabilityMatcher": "org.openqa.grid.internal.utils.DefaultCapabilityMatcher",
	  "registryClass": "org.openqa.grid.internal.DefaultGridRegistry",
	  "throwOnCapabilityNotPresent": true,
	  "cleanUpCycle": 5000,
	  "role": "hub",
	  "debug": false,
	  "browserTimeout": 0,
	  "timeout": 1800
}

Example 4: nodes and hubs in selenium grid

-we run this jar from 2 roles: hub and node
-hub receives commands Webdriver object of the client
-then hub is looking for available nodes 
 for execution.
-nodes are executing tests

Example 5: how selenium grid looks like

-it's a java program looks like jar file
-we run this jar from 2 roles: hub and node
-hub receives commands Webdriver object of the client
-then hub is looking for available nodes 
 for execution.
-nodes are executing tests