If you wish to provide Internet access to others using your router but don't want them to have access to your network then you can create a Guest Wifi to achieve this.
Go to the Network menu and then to the Guest Wifi submenu.
You can make multiple Instance of Guest Wifi but each radio (2.4Ghz and 5Ghz) can only have one active at any one time. You create an Instance by entering an instance name and clicking on the Add button.
This will create a default guest wifi instance using the name you provided. It has a SSID called guest, uses the 2.4Ghz radio, is not encrypted and has no bandwidth limiting.
To alter these values to suit your situation you click on the Edit button for that instance. This will take you to a customizing page where you alter any seetings you want.
You can change any of the settings such as SSID, use 2.4Ghz or 5Ghz, set encryption or set bandwidth limiting for the guest wifi. Click Save&Apply when done. Now return to the Guest Wifi overview page.
You can create as many instances as you like this way. To enable a guest wifi instance click on the Start button for that instance. Remember that only one instance per radio can be active at any one time. You will not be allowed to start multiple instances on a single radio. Stop the instance by clicking on the Stop button.
Your guests will now find a Wifi network that will allow them Internet access but will not allow them to access your Network.