The Heart Sutra introduces the bodhisattva known as Avalokiteshvara.
There are many bodhisattvas, but Avalokiteshvara is probably the most popular one of all.
He is chiefly popular because he is the bodhisattva of compassion, and so perfectly exemplifies that quality.
That means that if a devotee prays to this bodhisattva for help in any way, he will surely come to the devotee’s assistance.