Guest with two network interface

[mn]

I want to install a centos with two network interface. One is connected to the internet and the other will be used for some "pxe enabled" guests.
There are some documents on the web on how to configure for this purpose. However, I didn't find them useful!

In the VB setting, I entered host network manager and created a vboxnet0 with 192.168.1.10/24 and the DHCP server set to disable (Fig 1)
Then in the network setting, I enabled the first NIC for Host-only adapter (Fig 2) and the second NIC is set to NAT (Fig 3).

After booting the Centos, I ran ifconfig and saw enp0s3 which has no IP (I think this is the first NIC) and the enp0s8 which has 10.0.3.15 (which I think is the second NIC). I also see a virbr0 with IP 192.168.122.1 which I don't understand what is that!! (Fig 4)

Any idea about that?

[mn]

Fig 4 has been attached in this post.