these differences are called dialects. the dialect a person uses is usually decided by where they live. even though the dialects of english use different words or word order, they still have grammar rules. however, when writing in american english, grammar uses the rules of general american english. when people talk about using 'proper english', they usually mean using the grammar of general british english, as described in standard reference works. the models for "spoken" english in britain are often called received pronunciation or bbc english.