I want to know about infopath and also weather it is good to use instead of webparts or not ?
Infopath is a MS Office tool/program that lets you define and use XML based forms.
Start here with wikipedia.
Integration with SharePoint
The most common usage of InfoPath is to integrate it with Microsoft SharePoint technology using InfoPath Form Services (included in the enterprise commercial version of MOSS) or as the separate Microsoft Office Forms Server 2007 product. In SharePoint, a "Form Library" can be created and developed by using InfoPath. InfoPath fields will be exported as "Columns" in the library and can be directly read in SharePoint or be used as part of web services results in workflow development.
below link is "Introduction to Microsoft Office InfoPath 2007"
and "Integration of InfoPath with SharePoint"