If you are installing a self-rimming (drop-in) sink then you will have an option for the number of holes you would like the sink to come with. The number of holes you should choose depends on the type of faucet and accessories you are planning to install. You can purchase a faucet that requires one hole (single-handle), or three holes (separate hot and cold handle). However, if you are planning on purchasing an accessory as well, such as a side spray (vegetable spray), soap dispenser, or hot water dispenser keep; in mind they require a hole as well. Below is a chart of hole options and what they can be used for.
One hole: Allows for a faucet with a single lever handle (no separate hot and cold handles).
Two Holes: Allows for a faucet with a single lever handle (no separate hot and cold handles) and an option of a side spray, soap dispenser, hot water dispenser, or chilled water dispenser.
Three Holes: Allows for a faucet with separate hot and cold handles OR a single lever handle faucet with an option of two of the following accessories, side spray, soap dispenser, hot water dispenser, or chilled water dispenser.
Four Holes: Allows for a faucet with separate hot and cold handles and an option of a side spray, soap dispenser, hot water dispenser, or chilled water dispenser.
Five Holes: Allows for a faucet with separate hot and cold handles with an option of two of the following accessories, side spray, soap dispenser, hot water dispenser, or chilled water dispenser.
Most undermount sinks do not come with faucet hole options. When installing an undermount the faucet holes are drilled directly into the counter top just behind the sink.