Your Cisco network configuration is stored in two main locations: One is in RAM, and the other is in the configuration that is in use, or the running configuration. When you type commands, those commands are activated immediately and are stored in the running configuration, which is stored in RAM
You can use two commands to save your configuration, the write command or the copy command. The write command is deprecated, but would look like this
Router#write memory Building configuration... [OK]
The newer version of the command is the copy command, which looks like
Router#copy running-config startup-config Destination filename [startup-config]? Building configuration... [OK]
The deprecated command is short and single-purposed, not flexible with full options like the newer command.
For any command you only have to type as many letters as the IOS requires to uniquely identify the command. So you will find that a lot of old-timers use the following command as a reflex after they complete changes and when they exit Global Configuration mode to copy their current running-config to the startup-config:
wri mem
The copy command offers more flexibility and options. Not only can you copy the running configuration data to the startup configuration file, but you could copy it to a file on flash or to a TFTP server on your network. The copy command is only a little more to type:
copy run sta