From Distillers Wiki
Stills come in many designs. The most common stills are traditionaly made of copper, though in recent years stainless steel has made inroads in the industry. Almost all stills employ some sort of copper because it removes sulphates on contact.
A very detailed page on column still design is Boka_Reflux_Still_-_How_To_Build
There are two common designs of stills. The first and most common is the pot still which is used to produce whisky, brandy and other spirits which rely on flavor from the mash. Pot stills consist of a boiler, a condenser, and a lyne arm through which vapour travels from the boiler to the condenser. The lyne arm has a bend in it known as the lyne angle. Some pot stills have a thumper which serves to further purify the distillate. A heat diffuser can be used to prevent sorching inside the boiler
Aside from the common types of stills, There are other types as well. Bucket stills such as the amazing still, are used by some people to perform a stripping run before the product is refined in a potstill.
See also rectifier.