When you initially installed Slackware, the setup program invoked the netconfig program. netconfig attempted to perform the following functions for you:
It asked you for the name of your computer, and the domain name for your computer.
It gave a brief explanation of the various types of addressing schemes, told when they should be used, and asked you which IP addressing scheme you wished to use to configure your network card:
It then offered to probe for a network card to configure.
netconfig will generally take care of about 80% of the work of configuring your LAN network connection if you will let it. Note that I would strongly suggest that you review your config file for a couple of reasons:
You should never trust a setup program to properly configure your computer. If you use a setup program, you should review the configuration yourself.
If you are still learning Slackware and Linux system management, viewing a working configuration can be helpful. You'll at least know what the configuration should look like. This will allow you to correct problems due to misconfiguration of the system at a later date.