Kopitiam is Hokkien (I think) for "ka fei dian", a Mandarin term that translates to coffee shop. They are usually more akin to "stalls" then a "store", because most such establishments are part of a hawker centre.
In Singapore, most coffee shops are run by Chinese, typically a man slightly over fifty, wearing a white sweatshirt that barely conceals his pot belly and is probably beginning to bald. His smile is warm and friendly, and he handles the many different devices used to prepare your beverage with skill and grace. He also swears a lot, but then most people do when speaking in the Hokkien dialect.
While it is referred to as a "kopitiam", these coffee shops serve a lot more than just a cup of coffee. You can get tea, coffee, milo, as well as various soft drinks, and they also serve breakfast, which can range from roti pangan (roti kaya) to half-boiled eggs.
Even the drinks themselves come in different varieties. Here are some examples:
Perhaps I'll write some proper BNF to describe the ordering process one day.
From my own personal observations, the kopitiam "uncle" (ie. the shop owner) normally has two large "jugs", one filled with concentrated coffee and the other with concentrated tea. After an order is made, a cup already containing sugar is taken and filled with some of this concentrated beverage. Boiling hot water from a dispenser nearby is then added, and finally the various "extra" ingredients are mixed in, like milk. This process takes about less than 30 seconds.
The food and drink may be good, but it is also important to note the cultural significance of the kopitiam. Kopitiams normally open early in the morning, at around 6am, and serve the morning crowd who like to get a quick breakfast before going to work. The kopitiams normally have circular tables that can sit around 4-8 people, and so regular patrons of a kopitiam will generally befriend one another and sit together.
Later in the day, the kopitiam serves as a place to take a break and sip on some coffee while reading the newspaper, or chat idly with friends. In the late morning, especially, you will find many elderly folks (predominantly men) sitting there talking away, quite often with the shopkeepers as well.
As such, the word kopitiam nowadays is also used to describe any place where people congregate and chat idly and amicably. If you search for the word "kopitiam" on the Internet, you'll be likely to find many "cyber-kopitiams", which are basically web boards where free discussion is allowed and encouraged.
You always feel at home in a kopitiam.