Intentions are the linking of a piece of work to all the markets you 'Intend' to submit to.
Intentions are created from the intentions page of the Work details.
When editing intentions you are shown a list of markets that match the genre and length for that piece of work. These are selected (or deselected) and their priority set in the order they appear on the screen under 'Chosen Markets'.
On returning to the intentions page for Work you'll notice that each intention is listed with a
priority and either a black, blue or red block with it.
The 'ToDo' page shows the topmost priority available (Black) market when suggesting where something should be submitted to next.