Buffer: In Node.js to manipulate a stream of binary data, the buffer module can be included in the code. However, the buffer is a global object in Node.js, hence it is not required to import it in code using the required method.

It is a temporary memory in RAM that manages a block of data and sends it for processing, a buffer is a suitable very small-sized block for binary data, if the buffer is full then the data is directly sent for processing. Sometimes buffer is used as middleware between the processing of data and incoming because we need a processor for the processing of data but sometimes processor is busy in some other task so we need to transfer the data somewhere and need to be relocated. This requirement is met by the buffer. The Buffer class in Node.js provides access to allocate and use a buffer. And the buffer class is a global class so there is no need to import it. If you want to know more about Buffer then check out this article.

From : https://www.geeksforgeeks.org/what-are-buffers-in-node-js/