Hello Ram,
Please go through this eBook for theoretical aspects CACLCHR
Also go through all links here in SAP Help
Take Tcodes from this page Tcodes (Tcodes starting with 'C' are more relevant for PM).
Now, few lines about concept in SAP-PM usage:
A class identifies a group of Equipments having identical specification parameters (ex. AC Squirrel Cage Induction Motor). So Equipments of all such motors are assigned this class. (Class is created with CL02). The parameters I mentioned (Current, RPM, KW etc, etc) are called Characteristics in SAP. (These are created with CT04). The characteristics created so are assigned to the class (CL02). The Equipments assigned such class will show these characteristics (in the Class push button) and you will enter the values there. Some equipment will have 11 KW, 18A, 1440RPM and some 7.5KW, 12A, 950 RPM and so on. After having this master data exercise, you can search the equipments by the Characteristic values through Tcode IE05. Also, go through the Tcodes given above
Classes are used across modules, so it has Types. (002 is for PM, 001 is for Materials and so on)
KJogeswaraRao