Analog Digital Converters (also known as ADCs) translate your sound into the languate of machines.
In other words, they take an analog signal and translate it into a digital signal.
"Wow", you must be thinking.
"Is this the type of deep insight I can expect from the rest of this site?"
Hey, it's not my fault these names are so descriptive!
So with that in mind, let's look at a day in the life of a typical fan-favorite input signal: The Electric Guitar Riff.
During a filthy fret burner, you strum the strings of your finest solo-shredding axe.
The strings are put into physical motion by your inspired fingers. The vibration of the strings causes a current to be induced in the magnetic pickups of the guitar.
This electrical signal that is produced is analogous (sounds familiar right?!?) to the movement of the strings.
From here the electrical signal is sent to your computer where the full magnitude of its greatness can be forever preserved in digital form.
Ahhh, but computers only understand digital information. The solo is lost forever. The feast... it is ruined!
Have no fear! The Analog Digital Converter is here to rescue us and the eternal immortality of your solos.
This transformation between the analog and digital world takes place inside your Audio Interface.
Digital binary data is the output from the ADCs which can now be interpreted by your computer.
Once again - analog digital converters take the electrical signal from your instrument or mic and translate it to a digital form that can be used by your Digital Audio Workstation (DAW), which in this case is a combination of your home computer, audio interface, and recording software.
So by the end of it's journey, the physical movement of your hands or vocal chords are processed into a digital form that can now be saved to your hard drive.
The returning journey is just as simple.
The digital data returns back to an analog signal that can be reproduced by your speakers, creating the sound waves we detect with our ears.
Just as the Analog Digital Converters discussed above, Digital Analog Converters (DACs) convert the signal from digital binary data to an electrical analog signal.
The same process described above just happens in reverse when the digital data is played back from your DAW.
These are the things that take digital signals and transform them back into an electrical signal that we can pump out of our speakers for the world to hear.
The journey begins and ends with the signal as an audible sound, and only in between does it get recorded to your digital media.
So now that you understand what is going on inside these components, let's talk about a more fundamental question.
So how do you decide how many individual digital buckets to break down your analog signal into?
It all depends!
You'll read that a lot as we progress through the different aspects of the home studio process, but its important to learn now.
There is not a magical, 100% right answer for all musicians.
But there is a best solution for your needs.
To determine how many digital buckets (1's and 0's) required to adequately convey your analog signal we need to understand Audio Sampling Rates.
In short just remember that "CD Quality" is defined as 16-bit/44.1kHz.
Many of the Analog Digital Converters that come standard on today's Audio Interfaces are capable of 24-bit/96kHz which is an even higher quality.
But there's a catch!
As you can see, in order to produce a track for a CD with one of these setups you would actually have to convert down to 44.1 kHz for the final transfer to the CD.
For this reason I believe it's not worth the added expense to get the higher sampling rates, but rather a marketing tool used by the music companies to make you THINK you need this.
The bit depth is a different story, however, and the details are discussed more thoroughly in my Audio Sampling Rates page linked above.
I know some of this is terribly boring / obvious, but I promise it will be worth it later on when you are trying to troubleshoot your setup or make a purchasing decision.