Question

there is 和 have 有何区别？

Answer 1

there is 为存在有，某个地方存在什么东西， have 为所属关系，如某人拥有什么。

Answer 2

there is + 名词单数做主语：
------ There is a book on the desk.
there are + 复数名词做主语
------ There are a few books on the desk.

主语+ have / has - - - - -
We have a good time when we stay with you.
Tom has a new bike from his uncle.