How is it that even a native speaker of English can have an accent? Well the truth is that there are many different forms of an accent, and the fact is that everyone in this world speaks with an accent. An accent is merely your own filter of a spoken language through your internal phonetic system. When you are born you are exposed to your first language. Your brain learns to hear the various sounds that are produced in that language and then learns to produce those sounds or sound groups that the language entails. These motor patterns are established and reinforced through years of usage and become your internal phonological sound system. When a non-native speaker goes to learn a new language their brain is not wired to produce or even hear the different sound variations of that new language. In return, the brain filters the new language through the old, or first language, and we hear what's called an accent. What I just described to you is the process of acquiring a foreign accent.
When you meet someone from New York, or New England, they also often sound very different from you, say you were born and raised in Western Canada. This is what is described as a regional accent or regional dialect. The English language has many variations of pronunciation derived from local dialects of a specific area of origin, and is the result of different groups of people settling in North American in different regions at different times. Often, these variances do not cause a great deal of disturbance when different speakers of the language are communicating with each other, but occasionally cause misunderstandings in the pronunciation of certain words. Imagine hearing a New Yorker tell you they, "caught (or cot) some shut eye."
The presence of a dialectal or regional accent is much less of a priority when it comes to considering accent reduction. While all accents are unique and beautiful, there can be many instances where a foreign accent can make communication more difficult. This is especially true when discussing matters like business or health care. Often times, people ask me why would I want to help someone get rid of an accent. However, accent reduction or commonly termed modification, is just a set of skills that you can learn, to reduce the influence of your first language when speaking your new language.