That is the default wildcard to activate OSPFv2 on all the IPv4 interfaces of the device. Once the interface is enabled, it will start announcing itself to potential neighbors.
In production environments, you would like to use the most specific wildcard to match only the IP address of the interface you want to enable the process on: "net 10.3.1.5 0.0.0.0 area 1" as an example. In this way you can control the advertised networks and the interfaces on which you would like to become neighbors (passive interface would avoid the neighbor relationship while advertising the network).
Best regards !