The word 'experience' has two meanings: the first meaning refers to something that you've gone through in the past, while the second meaning refers to the knowledge you've learnt after you did something. When the word 'experience' is used as something in the past, it is a countable noun but when used as the knowledge one obtains, it is an uncountable noun. Now I'll show you how to distinguish the two. For example in the sentence: He has a lot of experience. Here experience is placed after a lot of, and it remains its singluar form, so we can tell that it is uncountable and thus the word experience here carries the meaning of the knowledge he learnt.
P.S. 例句欠水準(zhǔn)呀、、、、