The Book of Tehillim (Psalms)

Tehillim (Psalms) is one of the most read books of Tanach (the Scriptures) with 150 poems and songs covering historic events, prayers and inspiration. Jews throughout history have read Tehillim as the go-to book whenever they were in trouble or needed help. Who wrote the book of Tehillim? What do the poems speak about? Why has it become so central to Jewish prayer?