Hi Nani.
I don't want to seem too blunt here, but with a quick search on google or bing you could have found this in about 10 seconds.
Try this:
http://searchunleashed.wordpress.com/2011/08/24/understanding-crawled-properties-managed-properties-and-full-text-index-part-1/
and
http://technet.microsoft.com/en-us/library/ff621097(v=office.14).aspx
http://johnrossjr.wordpress.com/2011/03/18/creating-custom-managed-properties/
Just a quick summary.
A managed property links to a content type or user profile property.
A crawled property is one that exists in the search index and can be included in search results or search on. Crawled properties are the managed properties but are in the search index.
New managed properties only show in the index after a full crawl.
Thanks
Tim
