Who Wrote This Book?  David is traditionally seen as the author of most of the psalms.  Given what we know about ancient cultures, the writings were likely rearranged, added to, edited, and expanded across the centuries. This makes the modern notion of "author" not really relevant to these writings.

When it was Written:  Psalms spans centuries starting with Moses’ Psalm 90 to the post exile era in Psalm 126 when the Lord was praised by the return from captivity.

Introduction to Psalms:

The word psalms is derived from the Greek (Psalmoi), perhaps originally meaning "music of the lyre" or "songs sung to a harp" and then to any piece of music. Even odes meant to be sung with or without accompaniment.”

It is important to recognize that the psalms are not doctrinal statements, creeds, or history but that in ancient Israel, no less than in the modern world, poetry and music were the means by which people expressed the deepest of human feelings and emotions, the most profound of insights, and the most tragic and joyous of human experiences. They are both poetry and prayer, poetry intended to be set to music and prayed in worship.

The psalms were used by the Israelites in the context of worship to provide a structure in which they could bring their praises, thanks, hurts and grief honestly and openly before God. The Psalms were not thundered from Sinai or received in a vision. They are the prayers and praises of God's people preserved by the community of faith. As such, they have become authoritative for us: a guide for worship, an example of honesty before God, and a demonstration of the importance of prayer and meditation.

The Book of Psalms in its current, most commonly used form consists of 150 songs and prayers referred to individually as psalms and referenced by chapter and verse. They each have a poetic character with frequent use of parallelism. In addition to the title of the collection, which translates as "song" or "hymns" from both Hebrew and Greek, superscriptions (or headings) in many of the Psalms provide musical references and some direction, in some cases even references to melodies that would have been well-known by early congregations. Songs that can be identified as such in the Psalms include songs of thanksgiving (e.g., Ps 30), hymns of praise (e.g., Ps 117) and royal psalms, which may have been used in coronations and weddings. Identification of some psalms as prayers is also seen within the text, for example in the conclusion to Psalm 72, "The prayers of David son of Jesse are ended." The largest category of Psalms, though not grouped as such in the text, is that of lament (expressions of complaint and pleas for help from God). There appears to also have been an instructional function of the psalms as seen in their references to the law (e.g., Ps 1 and 119).

Dating of individual compositions is difficult, and in some cases impossible. Many appear to have been written early in the history of ancient Israel (first millennium BCE or even earlier), while others may have been written after the exile to Babylon, which occurred in the sixth century BCE. Biblical scholars note the early organization into five collections, paralleling the Torah or Pentateuch (the first 5 books of the Bible). However, other reasons for dividing the book in this way are unclear. Authorship is also uncertain in spite of frequent attributions to David.^[2]

the lovingkindness – mercifulness   (chesed) – goodness, mercy, with a strong emphasis of helping – of God. It appears 127 times in the Psalms.

Key Verses:

Psalm 22:10  “I was cast upon thee from the womb: thou art my God from my mother's belly.”

Psalm 96:1-2    1O sing unto the LORD a new song: sing unto the LORD, all the earth. 2Sing unto the LORD, bless his name; shew forth his salvation from day to day.

Psalm 96:3-5     [3] Declare his glory among the heathen, his wonders among all people. [4] For the LORD is great, and greatly to be praised: he is to be feared above all gods. [5] For all the gods of the nations are idols: but the LORD made the heavens.

Psalm 139:  13For You formed my inward parts; You wove me in my mother's womb. 14I will give thanks to You, for I am fearfully and wonderfully made.