Storage ?

Hi, I'm new to the forum. I bought a Venu, I would like to know the Storage environment. I connected Venu to the PC. I have seen that there are 3.6 GB of free memory. Connecting the Venu to Connect IQ, I see that there are 19 free slots for apps etc, for a total of about 18MB. The question is: of the 3.6GB free how do you use them, and why do I only have 18mb to host app dials etc. Can anyone explain to me the memory usage. THANKS