So to understand ram, you need to understand what a flip flop is. Those black boxes are just units of flip flops. These are transistors set up in such a way that they will either send a value out to a bus, let you over write the contents, or simply sit there.

So, a flip flop by itself holds either a value of 0 or 1, low or high charge. They are wired so that you have a number of them hooked together to send to a bus (a multi-bit wiring path). When your processor requests access to the ram, it will either allow you to read/write as desired or allow a read only depending on the port setup, but that is outside of the basics. Let's assume you can always read/write for now.

By sending an enable signal to the flip flop, or series of them, you enable them to receive a write command from the bus. Then on the next clock cycle, (basically a specified period of time determined by quartz oscillations), your enable goes low, and you activate the tri-state buffer (basically a little gate switch that allows the data in this flip flop to go out to a bus for use elsewhere, or to return the value to the processor for storage in a register. You can't send to it and receive from it on the same bus in one go because of bus contention (conflicting voltages and you risk unknowns or corrupt data.)

So on the silicon level, these are just pull up and pull down networks laid into the IC (integrated circuit, the black boxes as it were) if you are okay with the short version. These either connect to power or ground by a series of transistors that are high enable normally open, low enable normally open, or combinations of the above. Let's assume they can only be those two for now and not talk about crosses and other strange things you will find in a circuit diagram.

You should look up CMOS AND gate schematic and have a look to see what it looks like. The ones with an open circle close the switch, line into a line closes when receiving high. At the top will be power, the bottom ground. Follow the logical path there and see if the two inputs on the left, when both high, send a signal to generate an output of 1 on the far right side. If so, that means yes, A and B are both 1. Try it with other combinations of high/low and you will find that it only generates a 1 when both are high. 0 is low, 1 is high.

If you were looking for the electrical level, I'll bow out and let a EE give you a better idea of what goes on in there. This is the basics from a CE standpoint, with some simplification so that you don't have to go through the whole conceptual level of digital logic and circuitry to get to the 10,000 foot aerial view of RAM.

Just remember, ram is slow, ram is a long way from the cache, and ram is huge. It's for high capacity storage, the registers are where you put data from the ram to work with it quickly and efficiently before shipping it back off to be stored until you need it again.