Yes, address is the address of the computer in question, as in the computer where you are editing the file ^^
a netmask is a mask that is used to divide computers into subnets and specify the available hosts for every subnet
255.255.255.0
255.255.0.0
255.0.0.0
are default netmasks for the different IP classes.
"network" is the networks ID, and the "first" address is always the ID, while the last one (192.168.1.255) is the broadcast address, and on the broadcast address information is sent to all computers, for example if one computer is looking for a translation for a computer name, it can broadcast for it and get the answer from the machine that is owning the name. Or if a computer needs an address from a DHCP server and it doesn't have the DHCP servers address, it can boradcast and ask any DHCP server for a new address. The first one to answer is also the one that will give the computer a lease for an address.
EDIT: I might as well give you an example... =P
If you have a network where for example your router has the address "192.168.0.1" then that is the first available address in the network, since 192.168.0.0 is the network ID. The netmask for a network like this is usually set to 255.255.255.0 in a regular home network. It differs depending on what IP class you are using. Also in this case the broadcast address would be the last address, as in 192.168.0.255.
Well, you get the picture
