The C11 Standard, officially known as ISO/IEC 9899:2011, is a version of the C programming language standard that was published in December 2011. It introduced several new features and improvements over its predecessor, C99, including better support for multi-threading, enhanced type generic programming, and improved support for Unicode characters. This standard aims to provide a consistent and portable way for developers to write C code across different platforms. It also includes updates to the standard library, making it easier for programmers to utilize common functions and data structures, thereby improving code efficiency and readability.