What is the doxology?
The term "doxology" comes from the Greek words for "glory" and "word." So as a "word of glory," a doxology is simply a short hymn or expression of praise to God for his goodness and glory. In some sense, a doxology is what an entire worship service should be.
Many psalms are doxlogical, and many passages in the New Testament are as well and were likely sung (e.g., Eph. 1:3; Rom. 11:36; Eph. 3:21; Luke 2:14; Rev. 5:13). A famous biblical doxology often used to close worship services is Jude 24-25:
The church has also written non-inspired doxologies since the second century. For example, Gloria in excelsis Deo, based on Luke 2:14, has been in use for nearly two millennia and is in the Book of Common Prayer. This will look familiar:
Why sing a doxology in church?
The doxology which is often sung at UCC was written in the 17th century. As can be seen from the text, it praises the Triune God as the source of all blessing and calls all creatures to praise him:
There are good grounds for continuing to use doxologies in worship services. Doxologies are found in the Bible and have been in use for thousands of years in the church. As truth-filled words of praise, they glorify God. Like creeds, they also connect us to the church throughout history which has use these and similar words to praise God.
We usually sing the doxology after the offering. The offering itself is meant to be an act of worship, giving back to God was he has graciously given to us. A sung doxology helpfully reminds us that all of our financial provision comes from God, and that we are dependent on him from whom all blessings flow.
Some are uncomfortable singing the doxology because it may feel to "Catholic" or "liturgical." Of course, singing the doxology formally as a mere ritual without faith does not make one right before God (neither does coming to church, singing, or listening to a sermon without faith!).
But remember that part of the value of certain biblical traditions, and certainly our personal habits as training as disciples, is their repetition. And if there is anything worth repeating in this life, it is praising the altogether worthy Triune God!