A datacenter IP is an address inside a range operated by a hosting, cloud or server provider rather than by a consumer access network. Somebody rented the machine behind it.
What Spaw answers
is_datacenter is the flag and hosting_provider names the operator when a feed identifies one. The risk score carries +40, above a commercial VPN (+30) and well below an unallocated address (+100), a blocklisted one (+80) or a Tor exit (+70).
What it means and what it does not
A person signing up from a datacenter address is not browsing from their sofa: they are on a VPS, a scraper, a CI runner, or a proxy someone rented. For a consumer signup that is unusual enough to be worth a second factor. For an API caller, a webhook receiver or a business customer it is completely ordinary, which is why the flag is a signal with a weight rather than a verdict.
The important limit is the other direction. An address that is not flagged is not thereby a person's home connection — see residential proxy for what open data cannot see.