Identification
A wireless internet network's SSID is the alpha-numeric name given to that network when it is created, according to TechTerms.com. The SSID of a network can also be changed, and serves as a unique name to help identify the wireless network the PSP is connecting with.
Features
The SSID can be up to 32 characters long, and generally defaults to the name of the wireless router if no custom SSID is entered (e.g. "linksys"). When the PSP scans for available wireless connections, a list of each network is displayed, along with that network's SSID.
Benefits
A unique SSID of your wireless network enables you to quickly select that network from the displayed list when connecting your PSP to the internet. In short, it streamlines the connection process. The PSP may display multiple "generic" network names and will show all available wireless networks within range. Knowing your SSID is vital to quickly connecting the PSP to the internet.
Manual SSID Entry
According to PlayStation's Knowledge Center, you can also manually enter your wireless network's SSID. Select the SSID entry box when setting up your connection and pressing X. Press enter on the keyboard, then scroll to the next screen by pressing the right arrow button to allow your PSP to scan for the specific SSID.
Considerations
A WPA security key is needed to encrypt the network you plan to use for PSP internet access so other users cannot "hijack" your connection. The code for the WPA security key should be changed at least once a month.