а is typically used to connect parts of a complex sentence that are opposed to each other. Ia uchitel, a ona vrach (Я учитель, а она врач) - I am a teacher, and she is a doctor. i (и) is used to list a set of words (nouns like in this example, verbs, adjectives or adverbs), or to connect parts of a complex sentence that correspond to each other or "help" each other some sense. Ia uchitel, i ona uchitel (Я учитель, и она учитель) - I am a teacher and she is a teacher. Ia skazal privet, i ona ulybnulas' (Я сказал привет, и она улыбнулась) - I said hello and she smiled.
And = И, OR = ИЛИ. I'm learning English. Sorry for my English. Here you are need to write "AND".
Because it is not a brand name of a corporation (for example: L&M). They are living people. I am learning English. Sorry for my English.