Who is your Wali?

I was helping out my sister yesterday. She will be getting married sometime next year and she had all these forms from Religious Affairs that she had to fill in. Most people would know that she needs a 'wali'. I am not sure how to translate it. The closest I can came up with is 'guardian'. Anyway I was quite intrigued to discover that in her form, there is a list of 40 people or groups of people