How we speak is influenced by many things. Firstly, there is learning to speak English itself, where how we pronounce our words is all part of learning how to speak and copying the speech of those around us. If we are born into bilingual families, then we may learn to speak English alongside another language.  Then, as we go to school, we learn to read and to write a written equivalent of English speech that has standardised forms of spelling, punctuation and grammar, known as standard English.  Depending upon yourhome background, you may speak standard English with its associated accent Received Pronunciation (RP). Or, you may speak standard English with a regional accent such as that associated with Birmingham or the Black Country, and you might include a few dialect features different  from standard English, such as vocabulary (bostin for good) or grammar ( ay for I’m not)  in your speech.

 As we move across the country we experience not only changing landscape and architecture but also a gradual change in the sounds we hear, in the accents and dialects that relate to the place in which they are spoken and to which they belong. This phonomenon is known as a dialect continuum. The terms accent and dialect are often used interchangeably, although in linguistic terms they refer to two different aspects of language variation.
http://www.aston.ac.uk/lss/research/lss-research/ccisc/discourse-and-culture/west-midlands-english-speech-and-society/variations-in-english/