I was reading about the architeture of a RAM memory but now I'm confused about the use of buffer for input and output. Why I need to use this?
The data lines are used for more than one RAM module, so it it necessary to transfer data to/from the storage cells only when appropriate, hence the presence of chip select inputs to the buffers.
Voltage level translation is likely necessary, another function of the buffers.
The data to/from the storage cells may not all arrive at precisely the same time, so the buffers allow for some settling time, in conjunction with the output enable signal.
The write enable signal prevents data being written instead of read.