An inline method is a programming technique where the compiler replaces a method call with the actual code of the method. This can improve performance by eliminating the overhead of a function call, making the program run faster. Inline methods are often used for small, frequently called functions. In languages like C++ and Java, developers can suggest that a method be inlined using specific keywords. However, the compiler ultimately decides whether to inline a method based on factors like size and complexity. While inlining can enhance speed, excessive use may lead to larger binary sizes, which can negatively impact performance.