Distillation is the heating of a liquid to produce steam which is then condensed back into a liquid and collected.
One common example is the distillation of fermented alcoholic beverages to produce alcoholically stronger distilled spirits. Where fermented beverages can only reach a bit above 20% alcohol by volume (ABV) before the yeast die and fermentation stops, and even that only with specialized yeast strains, the standard strength in Western culture for distilled spirits is 40% ABV, and grain neutral spirits (a type of vodka) can be distilled to as high as 95% ABV, although spirits this strong should not be drunk without first diluting them, as they can cause significant damage to the mouth and throat otherwise. This increase in strength is possible because alcohol has a higher vapor pressure than water, and therefore has a lower boiling point. This does not, however, cause the alcohol to simply boil off first, and the water later - rather, the mixture boils at a temperature between the boiling point of alcohol and the boiling point of water, and the percentage of alcohol in the steam is higher than in the liquid that produces it.
The same factors that allow for a cleaner separation between alcohol and water (and therefore a higher final ABV) allow for a cleaner separation between alcohol and other fermentation products (known as congeners) that provide much of the flavor of the final beverage. Distillation to a higher percent alcohol by volume will therefore, assuming equal aggressiveness in discarding the foreshots (the earliest portion of the condensate to be collected, which is high in alcohol but also rich in congeners with a lower boiling point than alcohol, such methanol and esters), produce a more neutral tasting spirit. If this is taken "far enough," then the resulting spirit will be vodka, otherwise it will not, and what it will be depends on what the original source of carbohydrates for fermentation was, as well as whether anything was added after fermentation.