Encoding and decoding are terms used in various fields, including digital logic, computer science, and communications. Here are the definitions of encoder and decoder based on the search results:

• Encoder: An encoder is a combinational circuit that converts binary information in the form of a 2N input lines into N output lines, which represent N bit code for the input. It is used to convert an unambiguous piece of information into a form of code that is not so clearly understood. The device that performs this operation is called an encoder.

• Decoder: A decoder is a combinational circuit that converts n lines of input into 2n lines of output. It performs the opposite job of an encoder, which is to generate the original signal as output from the coded input signal. The device that performs this operation is called a decoder.

In computer science, encoding and decoding refer to the process of representing data in a different format for efficient transmission or storage. For example, encoding is the process of putting a sequence of characters into a specialized format for efficient transmission or storage, while decoding is the opposite process of converting an encoded format back into the original sequence of characters.

In deep learning, an encoder-decoder model is a widely used structure that allows a machine learning model to generate a sentence describing an image or perform other tasks. It receives the input, such as an image, and outputs a sequence of words.