Q:

What is the difference between ionic1, ionic2 and ionic3?  Is ionic2 and ionic3 are same? 

I have created project with ionic cli 2.2.1.  But when i enter into project directory and type "ionic info" it gives the following result. 
Your system information:
Cordova CLI: 6.0.0 
Ionic Framework Version: 3.2.1
Ionic CLI Version: 2.2.3
Ionic App Lib Version: 2.2.1
Ionic App Scripts Version: 1.3.7
ios-deploy version: Not installed
ios-sim version: Not installed
OS: Linux 4.4
Node Version: v6.10.3
Xcode version: Not installed
my project structure is
config.xml  ionic.config.json  package.json  resources  tsconfig.json  www
hooks       node_modules       plugins       src        tslint.json
Is this ionic2 project or ionic3 project. 

A:

What is the difference between ionic1, ionic2 and ionic3?  Is ionic2 and ionic3 are same? 

Wow, there are so many differences that it's hard to know where to start from.  No, Ionic 2 andIonic 3 are not the same. 
To see all of the differences, see the changelog:

https://github.com/driftyco/ionic/blob/master/CHANGELOG.md

This command:
curl https://raw.githubusercontent.com/driftyco/ionic/master/CHANGELOG.md | wc -l

gives 2687 lines.  There is a lot to read about. 
For a good start see:

7 Reasons Why Ionic 2 Is Better Than Ionic 1
What Does Ionic 3 Mean for Ionic 2?