Hello Debasish Roy 

Port cost - It is the cost of a port which is calculated by bandwidth of link and inversely proportional to bandwidth of link . The following table describe the port cost value for different bandwidth -

Path cost - The path cost is the metric stp uses to calculate the shortest path to elect root port to reach the root-bridge . The path cost is based on the speed of the interface of switch . The lower path cost path will be preferable and that switchport on which total cost is lower to reach root bridge  is called root port .

Have a nice day .