It's a call blocking service. You build your list which is a bit tedious but its rewarding when calls are blocked after one ring so doesn't stop first time calls. Landlines are free. Mobile is $2 a month. The only way to lookup a numbers is through the mobile app. Legitimate numbers being spoofed could end up being blocked.
Free service (for landlines), almost completely doesn't work. Blocks at most 1 in 20 or 30 spam calls.