Worship is the practice of devotion towards a god or groups of gods. It may be practiced individually, informally within a group (such as with prayer circles), or formally within a group (such as in a church).
Examples of worship
Adoration versus veneration
Catholicism and Eastern Orthodoxy distinguish between adoration, which is due to God alone, and veneration or dulia which may be lawfully offered to the saints. The external acts of veneration resemble those of worship, but differ in their object and intent. Protestant Christians question whether such a distinction is always maintained in actual devotional practice, especially at the level of folk religion.
Orthodox Judaism and orthodox Sunni Islam hold that for all practical purposes veneration should be considered the same as prayer; Orthodox Judaism (arguably with the exception of some Hasidic practices), orthodox Sunni Islam, and most kinds of Protestantism forbid veneration of saints or angels, classifying these actions as akin to idolatry.
Similarly, Jehovah's Witnesses assert that many actions classified as patriotic by Protestant groups, such as saluting a flag, are equivalent to worship and are therefore considered idolatrous as well.