A tune type (such as A major, reel) provides information about a tune: its tonic (key), mode, and form.
A tune page describes (in the title box) how the tune is typically played, as well as describing (in the list of recordings of the tune) how the tune is played on each recording of the tune. A recording page (in the track contents listing) describes how the tune is played on that recording.
The tune type information is intended to provide helpful information about a tune, but it should not be considered definitive or complete. In particular, the information about how a tune is typically played is subjective, based on my own, perhaps limited, exposure to the tune.
The tonic (key) and mode suggest both the scale used by the tune melody and the typical harmonies used to accompany the tune. The form (such as strathspey or reel) suggests the typical rhythm and tempo of the tune, often in terms of an associated dance form.
In a title box on a tune page, I name specific modes, such as major, minor, mixolydian, and dorian. I use mixolydian to indicate a tune that sounds major but uses a lowered 7th note (for example, G natural in a tune in A) and features the VII chord (for example, G major in a tune in A). I use dorian to indicate a tune that sounds minor but uses a raised 6th note (for example, F# in a tune in A) and features the VII chord. A few tunes are listed as double tonic. These are tunes that to me sound more like they switch between two major modes, such as A and G, than being in mixolydian mode (for example, they may use a raised 7th note when in A major, unlike a strict A mixolydian tune).
The assignments of tune modes are often subjective and may not be strictly accurate in a music theoretical sense. For example, although these terms refer to scales with seven notes, there are tunes that use scales of five or six notes or that do not limit themselves to any 7 note scale. In addition, as my understanding of these concepts is evolving, some tunes listed as minor I would now describe as dorian. Updates will be made eventually.
A shorthand notation is used in the lists: "A" indicates a tune in A major, mixolydian, or double tonic; "Am" indicates a tune in A minor or dorian. Flat keys are indicated using the letter "F", for example, "BF" is B flat.
Different parts of a tune can have different tonics and modes. I have listed the tonic and mode of the part of the tune I consider to be the first part, although the choice of which part is first may be subjective (different fiddlers may disagree on which part is played first) or incorrect (sometimes while playing a medley a fiddler may choose to start a tune with a part other than the first part).