Hi Akhilesh,
Let me try to cover your questions.
1. Altiris Application Metering Agent & Altiris Inventory Agent
These agents are used to provide the functionality of Altiris Inventory Solution.
You may refer to section 2 of the following page
https://support.symantec.com/en_US/article.DOC5719.html
Also there is a video available explaining how to monitor application using application metering policy
https://www-secure.symantec.com/connect/videos/monitoring-applications-client-machine-using-application-metering-policy-video
2. Altiris Inventory Rule Agent
This plug-in provides the functionality of Inventory Rules, Detection and Applicability Checks
You may refer to the following page for more details
https://www-secure.symantec.com/connect/articles/technical-white-paper-inventory-rules-detection-and-applicability-checks
3. Software Management Framework Agent
Please refer to this thread for detailed information
https://support.symantec.com/en_US/article.HOWTO62940.html