The `steam_api_ext64.dll` file, given its name and the incomplete metadata, appears to be an extension or a variant of the standard Steam API DLL used by applications, particularly games, that integrate with Steam's features and services. The "ext" in the name suggests "extension," and "64" indicates it's designed for 64-bit systems. This DLL likely provides extended functionalities or features beyond the basic Steam API, possibly including advanced integration with Steamworks features such as achievements, leaderboards, multiplayer networking, and user authentication. If there are issues related to `steam_api_ext64.dll`, such as error messages indicating that the file is missing or corrupted, users might experience problems with games or applications that rely on this DLL for Steam integration. Resolving such issues typically involves ensuring that the game or application is properly installed, verifying the integrity of game files through Steam (if available), or reinstalling the game or application to restore any missing or corrupted files.