@Bengari

Although Asif Yiusafzai has given an excellent outline but for details please see wikipedia. If you are student of economics you may well understand. If you have no background in economics then I have written a very simple explanation of global crisis in economics section, which may be helpful for you.

Pakistan economic situation is not directly affected by global economic crisis, but however global economic crisis has repercussions for our economy mainly in terms of decrease in exports.