A buffer temporarily stores data while the data is the process of moving from one place to another, i.e. the input device to the output device. You can say that buffer is a part of the memory. You can say that a buffer is a pre allocated area of the memory where you can store your data while you are processing it.
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The buffer, on the other hand, is found mainly in the RAM and acts as
an area where the CPU can store data temporarily. This area is used
mainly when the computer and the other devices have different
processing speeds. Typically, the data is stored in a buffer as it is
retrieved from an input device (such as a mouse) or just before it is
sent to an output device (such as speakers). However, the buffer may
also be used when moving data between processes within a computer.
So, the computer writes the data up into a buffer, from where the
device can access the data, as its own speed. This allows the computer
to be able to focus on other matters after it writes up the data in
the buffer; as oppose to constantly focus on the data, until the
device is done.
Buffers can be implemented in a fixed memory location in hardware or
by using a virtual data buffer in software, which points to a data
buffer are stored on a physical storage medium. Majority of the
buffers are utilized in the software. These buffers typically use the
faster RAM to store temporary data, as RAM has a much faster access
time than hard disk drives. A buffer often adjusts timing by
implementing a queue or FIFO algorithm in memory. Hence, it is often
writing data into the queue at one rate and reading it at another
rate.
Stack is a collection of items in which the data are inserted and remove from one end called the top of the stack.
In computer science, a stack is a particular kind of abstract data
type or collection in which the principal (or only) operations on the
collection are the addition of an entity to the collection, known as
push and removal of an entity, known as pop