:) Hi raidne,
As you have already stated, it really depends on where you go.

However I will generalize for you to give you some idea of the differences:

Reseller hosting;

You are required to:

Look after all your clients orders and invoicing.

Look after level 1 support for your clients, this is general support such as lost passwords, nameserver, domain names, how to's and some minor hosting issues.


Your Reseller hosting provider is required to:

Provide level 1 support directly to you and look after Level 2 support issues, this includes but is not limited to all server, hardware, software, security and network issues.


Dedicated Server;

Unmanaged:

You are required to do all the above with the exception of network issues.


Managed:

This varies from provider to provider and can be semi or fully managed;

Semi Managed;
Too varied to list here

Fully Managed:

Can vary from it being somewhat like a huge Reseller package where the provider gives level 1 support directly to you and looks after Level 2 support issues, this includes but is not limited to all server, hardware, software, security and network issues to just level 2 support.


Please Note: this is an extreme generalization and is dramatically simplified for obvious reasons.

So in short if you go for an unmanaged server you will require knowledge of running a server such as server, hardware, software and security and a lot more.