What is effect to me if my question or answers receive too much downvote?
The effect on you is that you lose "reputation".
Each time someone downvotes a question or an answer that you have written, you get -2 "reputation", but it will never drop below 1. This is explained in the Help Center.
A question with many downvotes is less likely to be seen by other users, so another effect is that it becomes less likely to attract an answer.
As pointed out in comments below, receiving consistent downvotes may get you temporarily blocked from asking further questions, and eventually even banned from asking any questions.