RAM means random access memory. A better name would be read/write memory. Ram is
VOLATILE, meaning that when you switch off, the data it contains is lost.
There are two main types of ram, static and dynamic.
Static ram uses flip-flops to store bits, and so consumes current whether they are storing a 1 or a 0. Dynamic ram uses capacitors to store charges and use less power.
However, these stored charges leak away and have to be continually REFRESHED which makes the circuitry more complicated.
The 4118 is an 8 bit x1k static ram having an 8 bit data bus, D0-D7.
Data can be written to, or read from memory, depending the state of the WE pin.
There may be several memory chips, so only one is selected at a time by taking
the CS pin low.