IP range: 0.0.0.0 - 0.255.255.255 (0.0.0.0/8) , IPv4
IP Range organization responsible: IANA - Local Identification
This range is also known as "Class A" and it contains 16,777,216 (16M) IP addresses with the first address starting at 0.0.0.0 and the last address of this range ends at 0.255.255.255.
When using the CIDR range (Classes Inter Domain Routing) classification it is also typical to call this range 0.0.0.0/8. Since IPv4 addresses are represented using 32 bits, this way of writing describes the range as all the addresses where the first 8 bits are preserved from the address 0.0.0.0. That means that there are 8 bits which are constant, and 24 bits that are changing. Hence, 16M addresses.
More inner ranges are usually associated seperately to different private organizations, so if you're interested in finding out which organization controls any specific inner ranges within this global range, you can browse deeper into the IP addresses themselves where we have a WHOIS tool that can reveal this information.