Here is the simple answer.
By God's foreordination I mean that God foreordains all that is to come to pass according to His eternal plan. God's ultimate plan is that His will shall be glorified. But note that I have just defined foreordination using the word "foreordains". That is not quite helpful is it? So let's be more precise and define foreordination without using the word itself. By foreordination, I mean that God predisposes all that is to come to pass and the conditions in such a manner that all shall come to pass according to God's eternal plan. These events may come to pass via the free actions of moral agents (both saved and lost) or via God's causative acts.
By God's foreknowledge, I mean God knows always and at all times everything which is to come to pass. Why does God know this? God foreknows what is to come to pass because, as stated above, God has prearranged the happening of what is to come to pass through the actions of free moral agents. Thus we say that God foreknows because He has foreordained. This last statement makes sense when we observe that when we say, “I know what I am going to do,” it is evident that we have already determined to do so, and that our knowledge does not precede our determination, but follows the determining and is based upon the determining. To admit foreknowledge carries foreordination with it.
The Scriptures speak of God’s perfect knowledge: Job 37:16, that He looks into man’s hearts, 1 Samuel 2:3; 1 Samuel 16:7; 1 Chronicles 28:9; 1 Chronicles 28:17; Ps. 139:1-4; Jeremiah 17:10, that God observes our ways, Deuteronomy 2:7; Job 23:10, Job 24:23, Job 31:4; Psalms 1:6; Psalms 94:9-11; Psalms 104:24; Psalms 119:168, Psalms 139:1-4; Psalms 139:15-16, that God knows the place of their habitation, Psalms 33:13, and the days of our lives, Psalms 37:18, Proverbs 8:22-23; Proverbs 8:27-30; Proverbs 15:3; Isaiah 40:13-14; Isaiah 40:27-28; Isaiah 41:22-23; Isaiah 41:25-27; Isaiah 42:8-9; Isaiah 43:11-12; Isaiah 44:7-8; Isaiah 44:24-28; Isaiah 45:18-21; Isaiah 46:10-11; Isaiah 48:3-7; Romans 11:33-36; Romans 16:27; Hebrews 4:13; 1 John 3:20.
The above is important because I have witnessed how many confuse the terms and concepts behind them. Foreknowledge presupposes foreordination, but foreknowledge is not itself foreordination. Misunderstandings of these terms have led the uninformed to claim that the related Reformed doctrines are fatalistic.
From these misunderstandings, we see incorrect statements such as the following:
Necessity of a hypothetical inference...
If God foreknew Peter would sin, then Peter cannot refrain from sinning. (Incorrect)
The interpretation above wrongly interprets God's foreknowledge as impinging upon Peter's moral free agency. The proper understanding is:
The necessity of the consequent of the hypothetical...
Necessarily, if God foreknew Peter would sin, then Peter does not refrain from sinning. (Correct)
In other words, the actions of moral free agents do not take place because they are foreseen, the actions are foreseen because the actions are certain to take place.
Bottom line, MC, don't confuse ordaining with direct causation.
AMR