After praising Allah and extolling Him with all venerations, prayers and everything good, we then direct our attention to the Prophet (peace be upon him) by saying, السلام عليك أيها النبي ورحمة الله وبركاته. This is usually translated as, “May peace be upon you , O Prophet, and the mercy of Allah and His blessings.”
The meaning of سلام can either be viewed as being one of Allah’s names meaning ‘The Source of safety and security,’ as if to say, “May Allah be upon you, protecting and taking care of you.” Or it could also mean ‘safety,’ as if to say, “May you be safe from every harm.”
We then mention the one whom we are addressing: أيها النبي - O Prophet. The word نبي is said to come from the meaning of very important and relevant news - and the Prophet (peace be upon him) was so-called because he informed about such news. Alternatively, it comes from the meaning of elevation, something that is risen from the earth, and the the Prophet (peace be upon him) would have been so-called because he has a higher, elevated status in the eyes of Allah.
After praying for the Prophet's safety and security, we also seek Allah's mercy for him with the phrase ورحمة الله - and the mercy of Allah. And we find that in any context where رحمة is paired with سلام , the word رحمة signifies any means through which one's goals are achieved, whereas سلام denotes the elimination of anything that is feared.
And we conclude our prayers for the Prophet (peace be upon him) with the saying وبركاته, commonly translated as “and his blessings.” The word بركات is the plural of بركة which refers to divine, abundant, eternal, everlasting, blessings and goodness.
So when we say, السلام عليك أيها النبي ورحمة الله وبركاته we are essentially saying, “May Allah protect you, take care of you, and safeguard you from every harm, O exalted messenger who delivered to us the most important message. May all paths that lead to good be opened to you, steering you away from the perils of Hellfire, and may you be endowed with perpetual and plentiful blessings and benevolence.