There's a difference between "и" and "a". "И" is mostly used in simple recitation of objects or actions. "A" can be roughly replaced with words "but", "while", etc., and often there's some kind of contrasting statement.
For example:
Я люблю фрукты и овощи = I like fruits and vegetables - you can't use "a" here, it's always "и".
Я люблю фрукты, а мой брат - овощи = I like fruits, and (=while) my brother likes vegetables.