AL-BAATIN-The Hidden One, Knower of the Hidden The Imperceptible

The One who cannot be seen in the way the creation can be seen. He is the One from whom nothing is hidden and who surrounds all things. He knows even the inner states, yet He is veiled from the creation’s perception.

Allah, Exalted be He, says, “He is the First and the Last, the Outward and the Inward; and He has full knowledge of all things.”(Surat Al-Hadeed 57:3)

The meaning of the name Adh-Dhaahir (the Outward) is the great and the elevated One who is above everything.
The meaning of Al-Baatin is the One who is nearest to everything and everyone due to His awareness of all the secrets, and what is yet more hidden. These two names are amongst those names of Allah which always come together, for absolute perfection is realised in their combination, and they cannot be used separately.

Benefits of belief in these names include the following:

Worshipping Allah, knowing full well that He is aware of everyone and everything in His absolute knowledge, greatness and power, and that there is nothing that is hidden from Him.
Steadfastly dedicating ourselves to worshipping Allah, Exalted be He, and turning to Him alone to grant our requests and fulfil our needs.
Purifying our inner selves, extolling Allah whose knowledge encompasses everything and being aware of His nearness to us.

The One who is veiled from our sensory perception. The One who is unseen, yet whose existence and essence are made known through signs.

The One who knows the inner states, inner circumstances and inner thoughts of all of creation.

The One who enters unseen into all of creation. The One who is concealed within all of creation. The One who is the secret inner companion.

From the root b-t-n which has the following classical Arabic connotations:

to be concealed, to lie hidden
to penetrate into, to be inside

This name is used in the Qur’ān. For example, see 57:3

tin and Zāhir are opposites.

Zāhir is that which is outward, manifest, apparent, visible.

tin is that which is inward, concealed, obscured.