A Provider is an abstraction of a connection to the Ethereum network, providing a concise, consistent interface to standard Ethereum node functionality.
The ethers.js library provides several options which should cover the vast majority of use-cases, but also includes the necessary functions and classes for sub-classing if a more custom configuration is necessary.
Most users should be able to simply use the Default Provider.
The default provider is the safest, easiest way to begin developing on Ethereum, and it is also robust enough for use in production.
It creates a FallbackProvider connected to as many backend services as possible. When a request is made, it is sent to multiple backends simulatenously. As responses from each backend are returned, they are checked that they agree. Once a quorum has been reached (i.e. enough of the backends agree), the response is provided to your application.
This ensures that if a backend has become out-of-sync, or if it has been compromised that its responses are dropped in favor of responses that match the majority.
Returns a new Provider, backed by multiple services, connected to network. Is no network is provided, homestead (i.e. mainnet) is used.