What exactly does Psalm mean, what is it?

In the Hebrew Bible, the book is called Se′pher Tehil‧lim′, meaning “Book of Praises,” or simply Tehil‧lim′, that is, “Praises.” This is the plural form of Tehil‧lah′, meaning “A Praise” or “Song of Praise,” found in the superscription of Psalm 145. The name “Praises” is most appropriate, as the book highlights praise to Jehovah God. The title “Psalms” comes from the Greek Septuagint, which used the word Psal‧moi′, denoting songs sung with a musical accompaniment. The word is also found at a number of places in the Christian Greek Scriptures, such as at Luke 20:42 and Acts 1:20. A psalm is a sacred song or poem used in the praise and worship of God.