As was mentioned upthread, virtually all modern potable water wells are drilled wells.
The residential well for my house is a six-inch diameter drilled well that is 350 feet deep. Residential wells are routinely drilled as deep as 500 feet in my area. Until you hit bedrock the well is lined with steel pipe. Once the driller hits bedrock, the pipe is not needed, and you just have a rock well all the way down. A well pump is lowered down to near the bottom with an insulated power cord, and a discharge tube. The power cord and discharge pipe are run over to the house, and inside the house you have an expansion tank and the power supply. The top of the steel pipe out in the yard is covered with a bolted-down cap to keep out contaminants.
Bedrock wells are common for single-family homes. Typical flowrates from such wells are 10-15 gallons per minute (gpm). The water is deep groundwater that seeps in from cracks in the bedrock. The water that comes up is typically very clean. My water need not be treated at all, but we do so for aesthetic reasons. (We have relatively high levels of dissolved iron). In many cases, deep groundwater is also relatively “hard” (i.e. high levels of dissolved calcium and magnesium carbonates).
Out in rural areas and the outer suburbs, residential wells (and septic systems) are fairly common.
The groundwater wells used by municipalities and public water companies, on the other hand, need to be able to produce hundreds of gpm to be viable. These wells are typically much shallower (~50 feet deep) and are drilled into the unconsolidated deposits above the bedrock. These wells are much more affected by surface contaminants than bedrock wells and the water must therefore often be treated in some fashion.
Municipalities frequently use surface water supplies as well, if available (i.e. reservoirs). This water is always treated for contaminants.