A Lambda Function is a small, anonymous function defined using the keyword "lambda" in programming languages like Python. It can take any number of arguments but can only have one expression. Lambda functions are often used for short, simple operations, such as sorting or filtering data, without the need to formally define a function using the "def" keyword. These functions are particularly useful in functional programming and can be passed as arguments to higher-order functions, such as map, filter, and reduce. They help make code more concise and readable, especially when performing quick operations on data collections.