IP address like (192.168.1.1/255.255.255.0) needs to be given and it is a number which is unique on the network.
IP addresses has two parts network address, (number of network on which PC is) and host address (unique number of computer on network). The network address or subnet mask is usually 255.255.255.0 in LANs. The 255s indicate the network portion of the IP address. So, 192.168.0 is the network this computer is a member of. The zero is PC client or host number, so 1 is the individual number of PC.
Host address has four octets and each value can be in range of 0 and 255 with number separated by a dot like 192.168.1.1 Each octet has 8 bits so, IP address is 32-bit number in dotted-decimal notation. IP address is of two types dynamic (given by a DHCP server) and static (manually assigned). Dynamically assigned addresses needs a DHCP server configured to assign the IP address and the IP address of DHCP server is configured on client
Gateway address is the IP address of PC which enables access to the Internet and should always be on the same network.
DNS server address is IP address of PC that takes care of domain name translation to IP address. As each PC on network has an IP address but humans browse internet by giving domain names (like www.google.com) but it is not an address on network so, it is translated to IP address of PC on network by DNS (Domain Name Service) servers and we connect to that PC on the network.