first verse of the Stotram (Praisal song of Shiva)

ॐकारं बिंदुसंयुक्तं नित्यं ध्यायंति योगिनः । कामदं मोक्षदं चैव ॐकाराय नमो नमः ॥१॥

Omkaaram Bindu-Samyuktam Nityam Dhyaayanti Yoginah | Kaamadam Mokssadam Caiva Omkaaraaya Namo Namah ||1||


Its first verse of the Stotram (Praisal song of Shiva)

In this we are Invoking and praising the value of "OM"

Because the creation have begun with the sound of "OM"

Lord Shiva was the first one who was created from the "OM" sound

He is not one of god but "Mahadev", meaning the Great God.

It's Meaning is:
1.1: (Salutations to Him) Who resides In the Spiritual Heart Center as Omkara, On Whom the Yogis Constantly Meditate,
1.2: Who Grants All Desires and also Liberation to His Devotees.
Salutations to that Shiva, Who is represented by syllable "Om"

Don't presume or think of "AUM" meditation as one of many ways of meditation, but know it as the King of Meditation, which if done with purity and devotion, it brings up the very spiritual world near to you.

Aum, is the mother of all Sounds in the world. It's importance is much more than any other Mantra in whole universe.