Cuts is the term used by distillers to describe the process of deciding which portions of the run are to be included in the final product. Making good cuts is essential to making a good spirit; it can mean the difference between a cheap, hangover-inducing swill and a top-of-the-shelf product.
Cuts are generally divided into four fractions: foreshots, heads, hearts and tails. They are not hard divisions. Smearing, the mixing of the fractions, causes all four fractions to flavor the whole run. Most spirits are distilled at least twice. The more a product is distilled the more compressed and distinct the fractions are. The negative is that it also reduces that flavor of the spirit.
Learning the Cuts
The best way for newbies to learn to make cuts is to collect everything from the run in small glass jars, let them sit covered by a paper filter overnight, and then smell and taste each bottle in turn. With more experience, distillers can learn to "cut on the fly", making cuts during the run.
Procure a good number of small (say 500ml) jars, number them, and get a big ol pot that is big enough to hold everything you'll want to blend. Collect your run in these numbered jars, and leave them to air out for a day or two with a coffee filter or similar over them to keep out the bugs and dust. Some of the more volatile and unwanted components will evaporate off over this time, and you'll be able to make better cuts and blends.
Stripping or Wash Run
The stripping run begins the separation of the ethanol from the water. Here you can make a Foreshot cut, but no other cuts are needed if you are planning a second Spirit run. There's no need to collect into jars here, one big container is fine. The output of this step is referred as Low wines. All of that will be put back into the still at a later date for the spirit run.
This is where you do a Foreshot, Heads, Heart, and Tail cut. For a spirit run the Heads and Tails are more compressed into the end jars. If you're collecting into jars you do not need to make cuts during the run. You will do that part later by selecting the jars you want to keep.