On this pageProxy_0 Git Source This abstract contract provides a fallback function that delegates all calls to another contract using the EVM instruction delegatecall. We refer to the second contract as the implementation behind the proxy, and it has to be specified by overriding the virtual _implementation function. Additionally, delegation to the implementation can be triggered manually through the {_fallback} function, or to a different contract through the {_delegate} function. The success and return data of the delegated call will be returned back to the caller of the proxy. Functions _delegate Delegates the current call to implementation. This function does not return to its internal call site, it will return directly to the external caller. function _delegate(address implementation) internal virtual; _implementation This is a virtual function that should be overridden so it returns the address to which the fallback function and _fallback should delegate. function _implementation() internal view virtual returns (address); _fallback Delegates the current call to the address returned by _implementation(). This function does not return to its internal call site, it will return directly to the external caller. function _fallback() internal virtual; fallback Fallback function that delegates calls to the address returned by _implementation(). Will run if no other function in the contract matches the call data. fallback() external payable virtual;