Q: I have just been initiated into japa meditation. I just wondered: is the mantra a sound or a word?
And if Atman and Brahman are one, I am interpreting that correctly to mean that in my deepest Self (soul) I am divine – at one with Brahman? And that that signifies a unity (oneness) not sameness (identity)?
To put it in Christian terms, in my soul the Spirit of God dwells (as Eckhart said: ‘the I with which I see God is the same I with which God sees me’ and ‘my ground is God’s ground, God’s ground is my ground’).
Thus Advaita: ‘not two’ (but not completely one either – monism). In Christianity: ‘whatever you do to the least of these, you do unto me’ (Matthew 5: 45).
A: ‘japa’ meditation is the mental repetition of a sound or a mantra. You could use the name of a god but it would still function as a sound. I.e. you are not supposed to ‘think’ about it, dwell on its significance etc. – that is a different form of meditation entirely. You give attention only to the repeating sound, ignoring any other thought. The repetition gradually loses its intensity and frequency and you are eventually left with complete mental silence. (May take a few years to get to this point!)
Atman and Brahman are two words for the same non-dual reality. The former is from the perspective of the (apparent) person and the latter from the as-if-perspective of absolute reality. Ishvara is the name given to Brahman from the perspective of empirical reality. Everything (including you and Ishvara) is simply name and form of Brahman. The relevant metaphor is that of bangle, ring and necklace being name and form of gold.
It would be best for you to temporarily forget all about Christianity and any other religion/philosophy until such time as you fully understand Advaita. Then you will be able to see that all the others are attempts, with varying degrees of success, to approach an understanding of the same truth. Trying to reconcile the views will only lead to confusion.

We all know that the shruti predominantly adopts the model of adhyAropa–apavAda (superimposition – sublation) in imparting the incommunicable Advaita message. There are other types of models and prakriyA-s also available in the scripture and tradition but they do not seem to be as popular. The adhyAropa–apavAda model superimposes an “imagined” or illusory creation on the really real Reality and as the student ingests the core Advaitic teaching, the superimposition is sublated. We find, however, that the shruti spends more time dealing with diverse aspects of the superimposed creation (birth, sustenance, death, action, fruits of action, rebirth etc.), the sublation being left to the ingenuity of the student as s/he reaches her/ his final understanding. One teacher estimates that Shankara in general devotes 90 percent of his time in most of his works on expiation of the Advaita doctrine and the attendant practices, leaving only a minor part on sublation and the outcome of the practices. This situation in some quarters has given rise to an insistence that the shruti teaches creation and that we have to take only the shruti vAkya-s and Shankara’s commentary on them as the pramANa (reference standard) for understanding the Advaita message forsaking other methods and vAkya-s in the scripture. Is that the intention of shruti? What is the final position of the shruti about creation from an Advaita perspective?