it seems there are 'home fee' and 'oversea fee'. What do they mean? What's the difference?

The difference between home and overseas fees is usually about double the cost. Home (inthis case probably UK resident citizens) students have government subsidised fees - overseas students are requiredto pay the full costs of the course.

Thanks a lot. I was told from the dept that they do not have any bursaries for phd students, and they ask for 8000 pounds/year (tuition fee). they will help me apply ORS, and if it is sucessful, I can only pay 3000 pounds/year. Does this mean that home fee is 3000 pounds and oversea fee is 8000 pounds?

Yes, the home fee is subsidised by the government, whereas the overseas fee is usually designed to make a profit.