Desire VS Attachment

What is desire? What is it attachment? Are they they same thing? If they are, is it bad to desire? If it's bad to desire, where to goals and basic needs like food fit in? Are they bad as well? Should I strive to want absolutely nothing, essentially erasing myself from existence?

This is a very common misunderstanding of the Buddhist teaching of "attachment", but can be very easy to clarify with a short analogy: I could desire to see a movie, and this is totally fine. If I end up missing the movie, there are 2 things I could do:

1. Just say "darn", go see it another time, and move on with life.
2. Act grumpy and pouty all day. 

The latter reaction is the one we want to avoid because it is an attachment to the reality where I didn't miss the movie. The former is the one that we should strive for in all aspects of our life.

Here's a couple of more serious real-world examples I've found in life:

• One day I am going to lose my wife. I'm not planning on it happening soon, but whether through divorce or death, it's inevitable that the nature of my relationship with my wife will change. Luckily neither of those are a reality in the near future, but when it does happen, I'll always remember the good times I had with her, but I'll have to do my best to let her go when either happens. I'll have to carry on with life and learn to be happy without her.
• When I was younger, I wanted to be a police officer. Up until I was about 13 I was determined to make them happen. However, as I started learning more about myself and the skills I found, I realized I am a very good graphic designer and not keen on putting myself in danger. I realized that being a cop likely wouldn't make me as happy as being a graphic designer would make me. I still had the option of ignoring that fact and being an unhappy cop, but that unhappiness is because I was attached to my goal of becoming a cop. I let go of that attachment and I became much happier as a graphic designer.

To summarize and simplify, desire is when you want things, and attachment is when you want things even when you can't have them or it wouldn't be the best thing to have. Buddhism is all about letting go of attachments when things change by accepting reality as it is and not what you want or to be.