this is how we pronounce words - how we make them sound. We all have an accent of some kind.

[If several people with different accents all read the same story aloud, each one sounds different although the story looks the same on the page. ]

Received Pronunciation: this is a phrase meaning the most widely accepted accent.

these are ways of speaking that involve different words, in sentences constructed differently and with different expressions.

[If several people each write a story in a different dialect, each version looks different on the page.]

Standard English: this is the most widely accepted dialect. It is not a better or worse dialect than any other, but it is the one that is used formally and the one you have to write in school most of the time. You can use it with any accent.