Radio waves have three characteristics that can be changed, Amplitude, Frequency and Phase. A mode is the way of changing electromagnetic waves.
By modulating waves, transmission of information is possible.
From amateur-radio-wiki.net there's a very brief but complete description of:
And from the same site an overview of:
- Ham Software
Digi modes
To get familiar with the different digi-mode signals there's a nice site giving 'waterfall' examples"
