What is the difference between summarizes and summarises? [duplicate]

Possible Duplicate:
“-zation” vs “-sation”?

Each post has an indicator which summarises who the post is shared.

What is the difference between these two terms?
Should I write summarises or summarizes?

Compare the results from the COCA (Corpus of Contemporary American English) to the results from the BNC (British Natural Corpus):

        Summarize      Summarise
COCA    1135               10
BNC      199              264

• Summarise is more common in British English, where summarize can also be found frequently.

• Summarize is more common in American English, where summarise is rarely used.

Note: this page in the Wikipedia contains a long list of words that end with "ize" or "ise" depending on whether the usage is American English or British English. You will find words like summarize(ise), organize(ise), authorize(ise) and many others there.