Here is a wonderful sermon/bible study I found from Mr. MacArthur explaining the difference between the church of God and Israel his chosen people.
http://www.gty.org/resources/sermons/1324/will-the-church-go-through-the-tribulation-part-1
http://www.gty.org/resources/sermons/1324/will-the-church-go-through-the-tribulation-part-1