Chill filtering is a method in whisky making for removing residue.
It works through reducing the temperature sufficiently that some fatty acids, proteins and esters (created during the distillation process) precipitate out and are caught on the filter.
This process generally impacts the taste of the whisky, by, for example, removing peat particles that contribute to the complexity, subtlety and smokiness of the flavour [citation needed].
For example, the Aberlour Distillery's distinctively flavored A'bunadh whisky, Laphroaig's Quarter Cask bottles, Kilchoman' s Machir Bay, and all of Springbank distillery's whiskies are not chill-filtered and are advertised as such.
Unfiltered whiskies chilled below a certain temperature can force some fatty acid esters out of suspension.