Could somebody explain these concepts? I am asking such question, because while studying JunFan/JKD, I found two different approaches to JunFan/JKD hand defence zones from two different JunFan/JKD instructors. One of them says that there are four corners ( or gates?) another that there are five. The first one also mentions outside high and low corner, which is lead side of the opponent and inside high and low corners - another side of the opponent. Instructor, who is talking about 5 gates, doesn't mention inside and outside at all. I would appreciate Your efforts. Thanks.

Its basically the same. Four Corners is the inside high and low and outside high and low areas of the opponent. The five gates is this, with the centerline included, which is the fifth area. This is commonly used in other schools, like my old TKD school, by instructors. While practicing the instructor calls a number and the student either defends or strikes that area.

Good info, Chen. I never knew what 5-gate theory was.

it is hard to me to understand that I should protect corners of the opponent and not my self, that these corners are not mine but opponent's. What is my problem?

Any help with this would be appreciated.

Perhaps you are looking too closely to the literal meaning of the words and not the concept itself. JKD is primarily a counter based system. Since that is the case, your movements, strategy and technique relies largely on what your opponent offers you. Therefore, they are not your corners but his, as you put it. And remember, defense includes offense.