Could you pls explain how to use 'if' in sentenses. my understanding is the word 'if' is used to say some which might happen in the future. So, when I speak I use 'if' in the following manner.
If he comes. But I have seen people saying 'if he came' please explain which is the correct one and please explain why.
I do not think you can use "if he came". It should be "if he had come" or (as you suggest) "if he comes". Came suggests that the action has already occured in which case there is no question of if it will happen.
Hope that helps. I am sure somebody can explain it more eloquently.
English verbs have only two tenses: present ("come(s)") and past ("came") -- everything else is a matter of participles used to show something we call "aspect".
But although we call them "past" and "present", that's not all they can do. The present tense form can be used to indicate something real, while the past tense form can be used to indicate something unreal.
"If he comes" usually refers to a possibility in the future, and it's a real possibility: there is a chance that he might come. "If he comes, we'll have a party."
"If he came", depending on the context, can mean:
1. A real possibility in the past: "If he came, I didn't see him." (It is possible that he did come, but I don't know if it actually happened.)
2. A hypothetical possibility in the present or the future: "If he came, it would be a miracle." (I do not believe he will come.)
Actually, the use of the past tense to indicate a hypothetical possibility is a very common thing. Peter, Paul and Mary were able to sing "If I had a hammer, I'd hammer in the morning", and some years later Midge Ure sang, "If I was a soldier, captive arms I'd lay before her".
Technically, it's actually the subjunctive mood, but in modern English the subjunctive mood is, in form, identical to the past tense. The only reminder of this is the alternate form "if I were", as in "If I were a rich man, all day long I'd biddy biddy bum" (Fiddler on the Roof), but even this form is dying out and being replaced by Midge Ure's "if I was".
The Supremes sang, "If I ruled the world, every day would be the first day of spring". Dean Martin wistfully crooned, "If you were the only girl in the world and I were the only boy, nothing else would matter in the world today". Some anonymous joker quipped, "If I told you you had a beautiful body, would you hold it against me?"
And then there was this classic exchange between Sir Winston Churchill and Lady Astor:
Lady Astor: "If you were my husband, I'd put arsenic in your coffee."
Sir Winston: "Madam, if you were my wife, I'd drink it."
There is the statistic that if all the Chinese people in the world jumped at the same time, it would cause devastating earthquakes (probably an urban legend, that one). If you took a chess board and placed one grain of rice on the first square, two on the second, four on the third, eight on the second and so on, doubling each time, then for the last square you'd need 18,446,744,073,709,551,615 grains.
And no doubt you use expressions like "If I had a penny every time he said that", or "If I were/was you".
What you've done, Holty, is to ignore the hypothetical meaning.
"If he came, it was a miracle" is the same as "If he came, I didn't see him" -- I am not sure whether he came, but it is a possibility.
"If he comes, it will be a miracle" means that you still think there is a possibility he may come (implying that you believe in miracles).
In the hypothetical version, "If he came, it would be a miracle", you exclude the possibility that he will come. It implies you don't believe in miracles, and are 100% sure that he will not come. You could add the phrase "(but he won't)" into the sentence:
"If he came (but he won't), it would be a miracle."
"If I had a hammer (but I don't)..."
"If I was a soldier (but I'm not)..."