These are probably among the most popular conditionals in English language. Students 'love' learning about them ;) I'd say - if you have an open mind and do not get discouraged straight from the beginning, you may find that those sentences can really come in handy in every day conversation :)
Let's give them a shot!
* The first two cases, namely PAST CONDITION + FUTURE RESULT and PAST CONDITION + PAST/PRESENT RESULT, TALK ABOUT SOMETHING REAL - NOT HYPOTHETICAL - that's why you shouldn't be surprised to find there PAST SIMPLE in the sentence after IF although it IS ABOUT THE PAST. However, this PAST really happened:
Francis really left at midnight yesterday, so he will probably be here by lunchtime tomorrow.
If Francis LEFT at midnight yesterday, he will be here by lunchtime tomorrow.
You really gave them all your money! You have made a big mistake!
If you GAVE them all your money, you have made a big mistake.
And LAST but not LEAST, a word from BBC ;)