What is the role of router and switch?

Router route packets based on IP addresses which are outside your local network.

where as Switch forward frames based on mac addresses  within your local network

Router :

1. Layer3 device .

2. based on IP address.

3. Checks routing table to get destination paths.

4. Routes packets to destination networks which are already learned through routing protocols.

Switch:

1.  Layer2 device

2. Based on MAC address.

3. Check MAC table to get in which port destination  device is connected.