DON'T (do not) is the negative form of DO while DOESN'T (does not) is the negative form of DOES. The tiny difference is: - Use DOES / DOESN'T if the subject is third-person singular (he, she, it). - Use DO / DON'T everywhere else.

Should I use don't or do not?

Don't is the shorter form of 'Do not'. In earlier days, at the time of writing, people used 'Do not' and while speaking, used to say 'Don't'. However, nowadays there is no such distinction and both the forms are used while speaking or writing.

What is difference of do not and don t?

Don't is the condensed form of the expression 'do not'. Don't is very frequently used in spoken English, whereas 'do not' is used frequently in written English. This is the major difference between the two forms.