What is the difference between the two? Too much other technical jargon being used on cisco's site to help me accutately understand. Thank you.
Edison, I am sorry - you are normally pretty good, but I think the way you have but this could lead to confusion.
SFPs ad GBICs do exactly the same job, and can work with the same media. The difference between them is physical. The SFP - Small Formfactor Pluggable - is smaller than a GBIC, and on equipment takes around the same space as an RJ45. SFPs are effectively replacing GBICs on new equipment, as you need half the panel space to fit one.
Take a look at www.sisteme-bis.ro/img_produse/imgprod_385.jpg for a GBIC and www.sisteme-bis.ro/img_produse/imgprod_384.jpg for an SFP. These two are both Single mode LX types. Also you can see that a different connector will be needed for an SFP, as the old ones are just too big.