L2TP connection

Hello for all mikrotik people there..!
Please anyone can tell me what is the benefit that we can achieve by L2TP connection..?
When we can apply the L2TP senario..?

L2TP is a VPN protocol. It depend on the scenrio that you have.

Example.
If you have some site to site that needs to be inter-connect so you can use the L2TP protocol to access both site vice versa.

so if my pc in a different ISP WAN connection can i apply this L2TP connection in this case ..? do i have to add any forwarding rule in my router..?

A typical application is using a third party vpn provider and going out internet from that provider instead of your local ISP.
VPNs are also used to remotely/securely access the home network
VPNS are used for workers to access work network or connect two work sites securely.