If you are ill,you should see a doctor.为什么等于When you are ill,you should see a doctor.

If you are ill,you should see a doctor.为什么等于When you are ill,you should see a doctor.
If you are ill,you should see a doctor是如果你生病了你可以去看医生,但是后面一句真的不明白,什么时候你生病了,你可以去看医生?
英霸帮忙解释一下最好可以全面一些