What is a DLL? How can it be used?

Okay, i've wondered this for a while now but not got round to asking the question (or thinking I need to use one). I'm about to create a large software suite and before I do so, am wondering if I could benefit from using these Dynamic Link Libraries. I've had a search on the Internet and can't find particularly useful information so to anyone who can answer any/all of these questions - thanks alot!

1. What is a DLL?
2. How is one created?
3. What can be stored in a DLL?
4. How can a DLL be edited both at run-time and design-time?
5. How can a DLL be accessed both at run-time and design-time?
6. How can you use a DLL?

Thanks alot in advance!
Jord

1) It is a self-contained module with executable functions and subs. It cannot be executed by itself (or in the general sense it can't)
2) VB allows you to make one. It is called ActiveX DLL
3) Same as in a regular application
4) Same as you edit a regularlar program as long as you have the source code
5) Define accessed as opposed from edited.
6) In you regular VB program you will declare one or more functions that are in the DLL then somewhere in your code area you will call that function.

In terms of 1 & 6, have you every used any References in your programs? (such as ADO, or Excel, etc.)

If so, those References are DLL's (well sometimes ActiveX EXE's, but being used as DLL's!).