Hi
Policy map decides what to do with a group once its traffic has been identified. This step can be considered the actual construction of a QoS policy-a policy-map in MQC terminology-by choosing the group of traffic (ie: class-map) on which to perform QoS functions. Examples of QoS functions are queuing, dropping, policing, shaping, and marking
Cisco MQC was first introduced as a framework for Class-Based Weighed Fair Queuing (CBWFQ) in Cisco IOS Software Release 12.0(5)T. It has evolved to support the majority of the QoS features. Using MQC requires a three-step process (see Figure 1):
1. Define a class-map. The first step in QoS deployment is to identify the interesting traffic (ie: classify the packets). This step defines a grouping of network traffic-a class-map in MQC terminology-with various classification tools: Access Control Lists (ACLs), IP addresses, IP precedence, IP Differentiated Services Code Point (DSCP), IEEE 802.1p, MPLS EXP, and Cisco Network Based Application Recognition (NBAR).
2. Define a policy-map. Decide what to do with a group once its traffic has been identified. This step can be considered the actual construction of a QoS policy-a policy-map in MQC terminology-by choosing the group of traffic (ie: class-map) on which to perform QoS functions. Examples of QoS functions are queuing, dropping, policing, shaping, and marking.
3. Apply the policy-map. Apply the appropriate policy-map to the desired interfaces, sub-interfaces, or Asynchronous Transfer Mode (ATM) or Frame Relay Permanent Virtual Circuits (PVCs).
do check this link for more info..
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fqos_c/fqcprt8/qcfmcli2.htm#1015614
regds
