This site explains it quite well: English Improvement
The inverted form is mentioned briefly.
Perhaps you could teach it by using situations that your students can relate to.
eg:
If he had spent more time studying he would have done much better in his English test.
= (He didn �t spend much time studying so he has done badly in the test.)
The inverted form isn�t used in everday speech. It�s quite formal.
Had he spent more time studying he would have done much better in his English test.
Occasionally you hear unreal conditional sentences that use subjunctive forms with inverted word order instead of the much more common "if" clause:
- Had I not tripped, I would have won the race. (= If I had not tripped, I would have won the race.)
- Were he alive, he would oppose your position. (= If he were alive, he would ...)
