Indicates conditions that rarely happens, it is sure to be mentioned in the if-clause is true or not. Or if the events in the if-clause, actual results will be as stated in the main clause, or it may be fictitious.
Displays the conditions that they say is not very confident that there will be an event that tells the actual it If-clause or if the events of the actual If-clause results will be as specified in the Main Clause, or it may be assumed.
used to indicate the conditions that don't say that I believe that there will be an event in If-clause that will happen or not or if an event in If - clause happened. will be as specified in Main Clause or it may be a fictional