An ETF Provider is a company that makes ETFs. When you go shopping in the supermarket there are many different brands for the same product. ETFs are the same, there may be many different ETF providers (or brands) that offer the same ETF (or product).
Some examples of the ETF providers we use at Moola are iShares and Vanguard. Both offer an ETF that tracks the FTSE 100 Index . The iShares one is called iShares FTSE 100 UCITS ETF and the Vanguard one is called Vanguard FTSE 100 UCITS ETF.
The ETF providers hire fund managers to manage their ETFs. For passive ETFs these fund managers will be responsible for making sure they buy all (or most) of the shares in the index and in the correct amounts. They then must maintain the ETF and make sure it successfully tracks (performs the same as) the index it’s supposed to be replicating.