Taps was chosen as the closing song for Guide meetings at the World Conference in 1920, and is still used for Guiding meetings and events. It is usually used with the standard lyrics, with the daylight lyrics being far less familiar. There are other verses, but they are not used in the UK. Equally, some countries use songs as a prelude to Taps, again this is not done in the UK.
The legend is that the name came from the tune being originally played on a drum. Later it was played as a military bugle call, each evening.
In the 1970s a group of US Girl Scouts wrote an alternative tune, which is used by some units under a variety of names (Carribean, Jazzy, Fast etc). In spite of this, the original is generally more popular.
In recent years some units have altered the final phrase, in order to make it more accessible for open units - a common alteration is to change it to 'Guides goodnight'.