What is the difference between a website and domain name?

Looking for a bit of help here. I went to start to make a website, and discovered I dont know the difference. I have read alot but the more reading i do the more confused I am getting. I hate to ask for help, (number one reason I am spinning my wheels here) but i am at the point i am stuck. I know the answer has to be really simple.

Here's what i am thinking. I want to start an authorihy site, (yep, will require lot of research) on nurtriion, healthy eating, organic, and non-toxic life style. I want to put an updated blog post 1 to 3 times a week.

I want to add several links, (an ongoing thing ) as i find them. I know not to overload those type of links, starting perhaps with 2 to 3 and gradually over the course of weeks/months gradually add more. I went to namecheap to look at getting a domian name and the one I thought of is dianajonesmiller.com and it is available. Then I came back to WA to see about a website and it also appears that dot.com would be good. But if my domain name is dianajonesmiller.com as an authorithy site how do i connect the dots to come up with a website that has a dot.com, dot.net, or dot. org. I am missing a vital piece of imformation here, sorry to sound so dumb.

I know I could add my nurtrition, diet extra sites as links but I dont know how to start the ball rolling.

In addition I have the following questions:

1. Can i add MLM links on my website/domian site or can I only add SEO links?

2. In the event I were to leave WA, (have no plans to) can I take my website with me if I have outside domain and hosting links?

Thank you guys in advance, maybe I can move on to the next step. I know what I plan or want to do will be an ongoing web deveoplement but i can see it in my minds eye.

thanks again