(請教英文語法) There is vs. It has

請問有人知道何時 只能用 There is 不能用 It has?

何時  There is, It has 都能用呢? Thanks a lot.

I have search some knowledge from Google and Yahoo.

It seems we need to identify the sentence means "own" or "exist" first.

If it is "own", then we can use "it has".

However, if it is "exist", then we can use "there is".

Some West people use another way to determine which is "emphasize" point of view.

Not sure if the above concept is correct or not. Please be advised. Thanks.

大家說得真好  有時孩子問我 中文 xxx...x 的英文要怎麼說或寫  我便回 yyy...y  結果她說 怎麼跟老師或書上講的不太一樣呢?  我只能回  我的美國同事  平常在email, document, 或 conf call 都是這麼用的  我看大家都這麼用  我就只好跟著用