I need to understand what export means

When you convert a thing into a symbol when the not basic option is selected there is a linkage to a action script and if you do select that it seems to make a notion in the symbol tree libary that list all the symbols contain in the project of the .fla flash application. Please explain in detail how and what this does and how to use it.

Now for my next question is if i have a symbol that i have used in my flash appication and i want to grab a complete copy of the symbol and all the actionscripts contained in the symbol and use it in a another flash application. What is the correct way to go about doing this safely with out lossing anything. Please explain in detail how and what this does and how to use it.

Which comes to my next question once i have a symbol sit in a folder or somthing else and i want to move that symbol into my new appicaltion again i ask what is the correct way to do this safaly with out looseing anything like the actionscripts.

And of course comes to my final question where and how should i maintain some symbols that i have created in the development of my flash application what is the proper methord of maintaining these symbols out of the appilaction. I have created some cool things that i can use in more then one application. THANKS