Non-compressor machines and compressor machines

NON-COMPRESSOR MACHINES
There are two main categories of ice cream maker, namely those with an in-built refrigeration unit (compressor, condenser, expansion valve, and evaporator), and those without. Most ice cream makers in the latter category have a removable insulated bowl that contains a sealed refrigerant liquid. Much like cooler ice packs, this bowl has to be left in the freezer overnight for the refrigerant liquid to freeze.

The main benefit of ice cream makers without an in-built refrigeration unit is cost: they tend to be cheaper than those with an in-built refrigeration unit. The main drawback is that unless you purchase a second bowl, you can’t make several batches or different flavours back-to-back; you’re limited to making just one batch of ice cream/gelato/sorbet per day and then have to clean and freeze the bowl overnight before you can make a second batch . Ice cream makers without an in-built refrigeration unit also tend to make ice cream and gelato that isn’t quite as smooth and creamy as that made in an ice cream maker with an in-built refrigeration unit.
Ice cream makers that use salt and ice, rather than a sealed refrigerant, to freeze ice cream also fall under this category

COMPRESSOR MACHINES
Ice cream makers in this category have an in-built refrigeration unit that freezes the bowl. The main benefits over non-compressor machines are that you don’t need to leave the bowl in the freezer overnight before it can be used, and you can make several batches, or different flavours, in the same day; you just clean the dasher and bowl after the first batch, place them back in the machine, and you’re ready to freeze the next batch. Ice cream makers with an in-built refrigeration unit do, however, tend to be more expensive.