This particular A/D converter, MCP3001, uses a SPI serial interface, after reading it's database, it all becomes very clear.
There are three pins connecting your microcontroller (the basic stamp) to the converter:
Clock, (aka "CLK", or "CK") is used to synchronize data transmission, it lets two different components send bits at the same speed, a single bit is sent in one clock cycle.
a clock cycle is putting the clock pin high (aka "on", "positive", or "+") then low (aka "off", "negative", or "-") , basically generating a square wave
Data, (aka "DAT", "DT", or "D out") is what outputs the reading values, it will output either a 1 or a 0 in one clock cycle, and your microcontroller stores that bit
Chip Select, (aka "CS", or "SS", SS means slave select, same thing though) is useful when you have multiple serial interfaced devices connected to just one microcontroller, only the chip that is "selected" will work, on this converter, putting the CS pin to high means not selected, while putting the CS pin low means you want to use that chip, and it begins to work
For A/D converters, sometimes the converter needs time to take a sample, for the MCP3001, you need to give it two clock cycles while it takes the sample, then the bits starts to stream in to your microcontroller, those are then stored in the memory of your microcontroller
The code will use the basic stamp's shift in command which makes this process easier, if you are using something else, you can manually make the clock high, read one bit, put the clock low, pause, and repeat until all 10 bits are read and stored
For more information, please read the MCP3001's datasheet
the images below are from the datasheet, READ IThttp://ww1.microchip.com/downloads/en/devicedoc/21293b.pdf