[Q] Purpose of network switches and bandwidth improvement

Hello guys and thanks for reading.

I'd like to ask if using a network switch improves the bandwidth of computer?

I'm planning to get a new motherboard as my CPU is dead and the LAN port of that motherboard is 1000Mbps my router have 4 ports of 100Mbps. If I were to get a network switch with 5 port, all 4 ports to the router and one to my computer. Will bandwidth increase? Not internet bandwidth but home network bandwidth.

Replying would be a big help.

Edit : Will the IP binded be the same on the computer? Cause I remember IP given from the router is different for every connection.