What is a sense amplifier and write enable?

[seriously disabled]

In Howstuffworks they write that memory cells alone would be worthless without some way to get information in and out of them. So the memory cells have a whole support infrastructure of other specialized circuits. These circuits perform functions such as:

 

• Identifying each row and column (row address select and column address select)

• Keeping track of the refresh sequence (counter)

• Reading and restoring the signal from a cell (sense amplifier)

• Telling a cell whether it should take a charge or not (write enable)

 

http://computer.howstuffworks.com/ram1.htm

 

What they don't explain is what a sense amplifier and write enable are.

 

Could anyone explain me in more detail what is a sense amplifier and what is a write enable?

Edited August 21, 2009 by Uri