SSID stands for service set identifier. It’s a technical way to refer to a network’s name. When you see a list of available Wi-Fi hotspots on your device, you’re looking at a list of SSIDs. They can be up to 32 characters long. Routers come with default SSIDs (SSIDs beginning with “TP-Link” or “Linksys” should sound familiar), but users can (and should) change them to whatever they like.
If you and your neighbor happen to both name your Wi-Fi the same thing, your device might try to connect to their Wi-Fi instead of yours. Because your neighbor probably password-protected their Wi-Fi, your device won’t be able to connect.
However, if a cybercriminal were to create an open network with the same name as yours, your devices would connect to it. This would allow the criminal to see what you do online and steal your private data.