what is Buffer. how it works

In computers, buffer is something which can be treated as an extra memory that can be used in future by the program. In most of the cases, buffer is used to enhance the program or to make it efficient enough for fast processsing. For example, if u want to allocate x memory in one statement, and after that y memory + after some more statement z memory....then it is good to allcoate x+y+z memory in statring of the program, here y+z memory is actually buffer that can be used by program in future. Hope this will be helpful to you. Ask if u have any query yet.

Your question is strange, infact it doe'nt makes sense (sorry if u r heart) but I will tell u what is buffer, normal meaning of buffer is space (kh'laa in urdu language) during execution a program needs space in RAM infact every running program needs space in memory, now this space is simply called the buffer

In computers buffer is the memory space where output or input data is stored temporarily.