Concatenation is the process of linking or joining together two or more items in a sequence. In computer programming, it often refers to combining strings, which are sequences of characters. For example, if you concatenate the strings "Hello" and "World," you get "HelloWorld." This operation is commonly used in various programming languages, such as Python and Java. In addition to strings, concatenation can apply to other data types, such as lists or arrays. For instance, if you concatenate the lists [1, 2] and [3, 4], the result is [1, 2, 3, 4]. This technique is useful for organizing and manipulating data efficiently in software development.