Ishvara: Personal-Creator God, Supreme Person (Gita)
Arjuna to Sri Krishna: I long to behold that form of Yours as Ishvara (Bhagavad Gita)
Bhagavad Gita Course - Dhyana Yoga Course
Ishvara can mean different concepts according to each Hindu philosophy, and also in the philosophy of yoga. It could be translated as the Creator God, the Supreme Person or the personal God.
Fifth Niyama of the Yoga sutras of Patanjali is Surrender to God (Ishvarapranidhana).
In Chapter 11 - The Yoga of the Universal Form of the Lord of the Bhagavad Gita, Arjuna tells Sri Krishna:
In chapter 11, Sanjaya say:
Universal Form as Ishvara, Yoga of the Supreme Person
In chapter 13- The Yoga of the Field, Sri Krishna tells Arjuna:
“Sri Krishna: When he sees that the same Ishvara remains equally everywhere, he does not harm himself, and therefore attains the highest goal” Bhagavad Gita 13.29.
For Gandhi:
“Whoever sees the same God everywhere merges in Him and sees nothing else; Thus he does not give in to passion, does not become his own enemy and achieves Freedom.” Gandhi.
“Whoever knows this mystery is not bound by activity, even in the midst of life. When we perceive this Supreme Presence that dwells in all beings, we cannot harm anyone.”
In Shaivism Ishvara is synonymous with Shiva (Maheshvara, Parameshvara, Supreme Lord - Knowledge of Brahman) or also with Ishta-deva (personal god).
For Vishnuists, it is synonymous with Sri Krishna or Vishnu.
For Bhakta Yogis, Ishvara is one or more deities preferred by the believer.
In the yogic school of Hinduism, it is any “personal deity” or “Spiritual inspiration.”
Ishvara Bhagavad Gita 
Ishvara.
The rest of this summary on “Ishvara” is available exclusively to students of the Bhagavad Gita Institute
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