Standard and nonstandard English

Can anyone explain this quote from Trudgill for me;

“1. Standard English fails to distinguish between the forms of the auxiliary forms of the verb do and its main verb forms. This is true both of present tense forms, where many other dialects distinguish between auxiliary I do, he do and main verb I does, he does or similar, and the past tense, where most other dialects distinguish between auxiliary did and main verb done, as in You done it, did you?

Trudgill (in Bex & Watts, 1999 : 117 – 128)

Bex, T. & Watts, R.J. (1999) Standard English: the widening debate, London: Routledge, [online], Available: http://www.phon.ucl.ac.uk/home/dick/SEtrudgill.htm

Accessed 17/02/11

The more I read it, the less it seems to make sense, can anyone decipher this for me?

Thanks.