What it actually means
Digital voice, sometimes called VoIP or IP voice, sends your phone call as data over the internet rather than as a signal down a copper wire. In a home it usually means a handset plugged into the back of your broadband router, or a small adapter, or an app on your phone or laptop. In a business it might be a desk phone, a softphone on a laptop, or a hosted PBX that routes calls to wherever your team is working.
The headline points are simple. Your number stays with you, even if you move house or change provider. You can keep the handset you already own in most cases. You can take the same number on multiple devices, so a call to the home number can ring the handset and your mobile at the same time. The trade off is that digital voice needs broadband and mains power to work, which matters if there's a power cut.
At home
What this looks like in the house
Most households don't think about the landline until something goes wrong with it. The first hint with digital voice is often a Sunday evening when the broadband is having a wobble and suddenly the home phone has no dial tone either. Or grandma tries to ring on the old number and gets nothing because the router was unplugged to fix a streaming issue. It's the same number, the same handset, but it now lives or dies with the broadband, and a household that's never had to think about that needs to.
In business
What this looks like at work
For a business the upside is real. One number can follow the team between the office, the van and home working without anyone needing to know the difference. The risk is the call your customer made on a Tuesday morning that hit nothing because the broadband dropped and there was no failover. A missed inbound enquiry from a buyer who was ready to spend is felt money. For shops, salons, garages and trades the till and the phone often run on the same circuit, so when the line goes down so does the booking diary.