The Sim card is the plug in chip that tells your phone what it is and whose the service provider is, etc.
But, different phones have different size chips... like an SD card on a computer... a new micro-SD might not fit or be useful on an older machine without an SD adapter ?
With a Sim you can plug a new chip into your old phone and keep using it... don’t need to buy a new phone... so “3 Way”
here means you get a Nano SIM card with Micro and Standard SIM adapters... so it should work on the phones in the market that are working now.
OK. For years I’ve switched an extremely small (nano?) sim card between my BlackBerry Priv and BlackBerry Classic often, so I understand that part. It’s the 3-way I didn’t understand. Now I get it. Thanks!