AL-‘ALEEM-The All-Knowing, The Omniscient The All-Knowing One

The One whose knowledge (ilm) is neither acquired through learning nor preceded by ignorance, nor followed by forgetfulness. He is aware of all things, even before they happen! The One nothing is absent from His knowledge.
Allah, Exalted be He, says, “Allah is All-Embracing, All-Knowing.” (Surat Al-Baqarah, 2:115)
“[He is the Knower of the Unseen and the seen.” (Surat Al-An’aam, 6:73)
“You are the Knower of the things unseen.” (Surat Al-Maa’idah, 5:109).
These names mean that Allah’s knowledge is comprehensive and extends to every thing seen and unseen, apparent and hidden. He also knows the past, the present and the future, and nothing whatsoever is hidden from Him.
Allah’s knowledge is all-encompassing; with Him are the keys of the unseen; He knows all that people’s hearts conceal and what their souls whisper to them. He also knows all about their circumstances and what is bound to improve their condition. He is aware of the laws He has sent down and those He has abrogated, and thus the ones which will benefit His slaves.

Benefits of belief in these names include the following:

Fearing Allah, being aware of His presence in public and in private, obeying His commands and staying away from everything He has prohibited.
Believing in divine destiny and experiencing peace and tranquility as to whatever Allah decrees for us.
Accepting Allah’s judgements and fully submitting to them, for they come from the All-Knowing, who knows what benefits His slaves and what causes them hardship.
Hoping for Allah’s mercy, experiencing peace and tranquillity in His presence and overcoming despair when adversity strikes.
Doing one’s best to acquire beneficial knowledge, demonstrating humility for Allah’s sake for having it, not boasting about it and teaching it to others, for all knowledge comes from none but Allah.

The One who comprehends everything. The One who is intuitively aware of all things, even before they happen. 

The One who knows with certainty. The One whose knowledge of past, present and future is deeply rooted and complete in all respects.

One from whom no knowledge is concealed. The One who is aware of the complete details of all matters. The Omniscient One.

From the root ‘a-l-m which has the following classical Arabic connotations:

to have knowledge, be cognizant, be certain
to be aware, thoroughly informed
to be find out, gather information
to have intuitive knowledge
to have firmly rooted knowledge of  the minute particulars
to act according to knowledge

This name is used in the Qur’ān. For example, see 2:32

Related names:

‘Alīm denotes knowing with certainty, especially intuitive knowing, omniscience.

Khabīr denotes an understanding of the inner qualities, secrets and true reality.