I will speak as an IT guy...
the co-location term is generic and implies your server is being co-located at a data center facility along the servers of a hosting provider and that you are renting floor space(cages) or rack space.
you are assuming co-location, as a term, is specific to HFT/LLT.. and it isnt, it has existed for a long long time...
yes, you can co-locate at the exchange data centers, but that is because the exchanges are selling rack space within their data centers (or cages in some cases as we have) as you have stated...
hosted solution, what it actually means is that the hosting provided owns the hardware and you are renting resources on that hardware... also known as Dedicated...
again, co-lo was a term even before it became popular with the financial services firms... and was in use even before that...
so co-lo = floor/rack space (where you provide your own network fw, and at times even the network conn you want (carriermeets), and servers) and hosting = dedicated servers, vps, jails, etc..
Quote from garachen:
I think people are conflating the terms 'hosting' and 'co-location'.
A 'hosted' solution means that your server is near your execution provider. Maybe orders are getting routed over the public internet to your execution provider or maybe there's a private line. This is fairly cheap - like hosting a website. About $100 a month
'Co-location' means your server is in a very specific building - the same one where the exchange matching engine is located. Space is rented by the rack but some providers will lease out slots. You have direct 10GB lines to a ISV - provided execution gateway (in the same building) or you have written directly to the exchange. As you might imagine, this is not cheap. Depending on exchange connectivity the first server can cost $2000 - $8000 per month but if you have a lot of servers the incremental cost gets much lower.
For most people a hosted solution is the way to go. It reduces your exposure to power and internet outages and increases your speed a little bit.