That is a good question.

Anxiety for me is excessive worry. Sometimes it can be about something lagitimate or the "what ifs". I try very hard to notice triggers for my anxiety. I beleive once I can take notice of that, then I will be able to deal with my anxiety in a more productive manner. I also suffer from OCD so my intrusive thoughts can also spin me right into an attack and that is very hard for me. Over time it has gotten a bit easier for me to notice my thoughts, realize they are just thoughts and let them slide away as easily has they came in. Like a Teflon pan. I try to have Teflon thoughts. I'm no master at this by any means but I try and most of the time I have success.

Stress........ARG!!! For me stress is about a specif issue. It weighs on my mind heavily. I beleive I am the biggest source of my stress. I place a tremendous amount of pressure on myself in most situations.
I think that if a person experiencing stress from a job or something in their home life, and they dont deal with it can eventually turn into anxiety. Like my job for instance. I used to stress myself out about deadlines. About never calling in sick. About being perfect. Yes I actually thought I had to be perfect. So after 4 years of this behavior, it caught up with me. I couldnt be all those things anymore and I literally fell apart. It caused me anxiety so overwhelming that I have to take medical leave to deal with those issues and many other issues I had been neglecting.
I hope this made sense. I have a hard time getting my thoughts out. Of course I havent had good sleep in days so maybe thats it too. LOL. I'll probably think of other things to add later but thats all I have for now.