I don't know umefika wapi so far, but let me try give a very broad overview.
what happens is that you can opt for your own short code, or to share an existing one.
the former is more expensive, but it enables you to control the short code and what comes in or goes out, and for the latter you will have to work by some rules. e.g
if you get your own short code say 11111, then people can send in messages like;
iko nene
funny pictures
nani mwenye wazua
2pm gang ....
and since the short code ni yako you can reply to the request in whichever way you want.
using a shared code there has to be a way of recognizing wainadi and thus the above becomes
wai iko nene
wai funny pictures
wai nani mwenye wazua
wai 2pm gang ....
the money part depend on if you want reverse billing ama the kawaida one, reverse billing chiucks cash from a users account wakipata sms, while the kawaida one a person anatolewa pesa akituma sms.
revenue is shared between the provider (short code owner) and the telco, I am not sure of the percentage lakini nasikia siku hizi its something close to 50/50, back when tis thing was starting it was 80/20.
For the shared code it becomes tricky since you have to resolve issues of sms sent that are ambiguous.
what else ...
I think the provider provides for the technical work, i.e code development and db stuff