Types of Storage
This is your external/internal hard drive. It stores bites of information in tiny packages that are ready by the hard drive which spins to read it at a very fast rate. The read/write heads do not touch the discs.
Cost: About $.05-$.10 per gigabite
This is your CD/DVDs. The discs hold a long line of code stored in bumps that translate to 1s or 0s. The laser in a CD player read these bumps to interpret the code.
Cost: About $.02-$.04 per gigabite
This is something like a memory stick or USB drive and it is very confusing in how it works. It has something to do with electrons and electricity and it is non-volitle meaning it can maintain the memory without power. It is fast and portable and this is why it is a preferred method to a CD/DVD storage.
Cost: Between $2-$5 per gigabite