"Even when I walk in the valley of the shadow of death, I will fear no evil for you are with me; your rod and your staff, they comfort me" (Psalms 23:4). 

This is one of the most beloved and well-known psalms in the Old Testament, according to faith leaders. 

Here, the faithful sense the doom of death along with the assurance that we are not alone as we approach the end of our lives.

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But what are the psalms — and why is this psalm so well-known?

The psalms "comprised the ancient hymnal of God’s people," according to Insight.org, a website that shares teachings from the ministry of well-known pastor and Christian broadcaster Chuck Swindoll. 

The poetry was "often set to music," that source also says.

"The psalms express the emotion of the individual poet to God or about God," says the website.

Different types of psalms were written "to communicate different feelings and thoughts regarding a psalmist’s situation," it says as well. 

Psalms of lament "express the author’s crying out to God in difficult circumstances," the website adds. 

"Psalms of praise, also called hymns, portray the author’s offering of direct admiration to God."

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Thanksgiving psalms usually "reflect the author’s gratitude" for deliverance from God, it notes.

Other types of psalms are referred to today as wisdom psalms, royal psalms (referring to Israel’s king or Messiah), victory psalms, Law psalms and songs of Zion, the site points out.

King David, in writing this particular psalm, is teaching that when a person is walking in the valley of death — "a place of darkness" — God is "with us in the darkness." 

That's according to Rabbi Pinchas Taylor, founder of The Ark Torah Study and Coaching Program based in Plantation, Florida.

God is "closer to us" when are in these dark times, Rabbi Taylor told Fox News Digital.

"Two verses earlier in the same psalm, in speaking of tranquil times, King David uses the more distant, third-person form to speak of God: 'He makes me lie down in green pastures,’" he also said.

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Only when King David turns to speaking of "times of travail" does he switch to address God directly, in the second person: "'You are with me,’’ said Taylor.

He emphasized, "There is no time when God is closer to us than when we are in pain."

Taylor said this psalm "emphasizes the importance" of God’s role in our lives. 

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"We are created in the divine image, and thus, God accompanies us throughout all the vicissitudes of life," he said.

"Our triumphs he participated in, but also our battles are his battles, as well as our difficulties, our fears and our darkness," he said.

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Rabbi Taylor also pointed out, "When a person realizes that God is with him, he realizes that he has the most precious and valuable gift imaginable, and thus, as the verse says, nothing troubles or worries him."

Stay tuned for more Bible verses of the day during the Advent season. To see yesterday's Bible verse, click here.