Phrases
A phrase is a bunch of parameters bundled together.
A Phrase is a bundle of one or more Parameters that create (or alter) a musical expression. It is useful as a coherent unit that can be moved, copied, edited and collected in libraries. Phrases are the building blocks that make Music Prototyping possible.
Phrases produce different output depending on the context in which they are used. Most phrases can be used in any Arrangement with any Harmony parameter to produce musically meaningful (and often surprising) results.

The most visible parameter Figure uses symbols that are relative to the Harmony parameter. Always keep in mind that without a harmonic context a figure can't produce audible pitches. Since almost every parameter influences MIDI output in some way, there is no way to tell in advance which MIDI notes a phrase will ultimately produce before all of an arrangement's Containers and parameters have been considered. That's why Synfire renders all of an arrangement from scratch every time you changed something.
Parameters & Clips
When a phrase is put in a Container we get a Clip. Looped parameters repeat only until the end of the container they are wrapped in. The phrase is literally "clipped" to the size of the container. By resizing a clip, you can determine how long a phrase is supposed to play.
When you build an arrangement it is common to put multiple phrases in the same container together (e.g. "Verse", "Chorus", "Reprise", "String Section", etc). Each phrase appears as a separate clip on the Tracks page.