The BRCK is a router, a WiFi access point that you can connect your computer or phone to. The BRCK is also a modem, that uses Ethernet, wireless (SIM card), or WiFi bridging to connect itself to the internet. (simply, you connect via WiFi to your BRCK, but the BRCK also needs to connect via some other channel to the rest of the internet.)
We've tried to break this down to be as simple as possible for you to see and manage. When you turn on your BRCK, you'll see this screen (seen below as mobile and as desktop sizes).
Initially, on the first-time setup of the BRCK, we prioritize the connection to the least expensive source, starting with Ethernet, then WiFi bridge, then your local SIM card, then our BRCK Net SIM card. Later, you can go into each individual BRCKs setting and prioritize these for yourself.
Ethernet - You can plug an internet-connected ethernet cable into the the BRCK and then use the BRCK WiFi signal for your connection.
WiFi Bridge - If there is another WiFi network in your area, you can log into it through the BRCK. Then you can use the BRCK WiFi signal as the connection to your own devices.
Local SIM - There's a SIM card slot on the side of the BRCK, which uses full-sized SIM cards. You can buy any GSM SIM card in your own country and plug it in here. Make sure that it is data-enabled, and that it has some kind of internet credit or bundle, and then use that as your source.
On this page, you can adjust the details of the connectivity options and change the settings for it by clicking on "view".