This is the 1602nd most frequent Japanese word.
御
Honorific prefix meaning "honorable" or "revered."
In this sentence, '御' is used to indicate respect or politeness in '御手洗', meaning 'honorable restroom' as a polite term for 'restroom'.
御手洗の場所を教えてください。
Could you tell me the location of the restroom?
Here, '御' is used in '御礼状', elevating the formality by making the acknowledgment of gratitude more respectful.
御礼状を書きます。
I will write a letter of gratitude.
In this example, '御' in '御幸せ' adds a polite tone when talking about someone's happiness.