Most American golfers - and I am one - have never seen a links course ... except for the ones we see each year while watching the British Open.
The British Golf Museum says that "links" are coastal strips of land between the beaches and the inland agricultural areas where crops are grown. This term, in its purest sense, applies specifically to seaside areas in Scotland.
So "links land" is land where seaside transitions into farmland. Links land has sandy soil, so crops can't be grown.
The land, in fact, was thought to be worthless because it was not arable for crops.
But back in the mists of Scotland, someone got the bright idea to put a golf course on that land. What else where they going to do with it? And links golf courses emerged.
Because they were close to the beach, lots of sand traps were a natural (the soil was very sandy, after all). But the traps had to be deeply recessed to prevent sand from being blown away by the constant wind. Because the soil was of a poor quality and constantly buffeted by the seaside winds, not much would grow on it - mostly just tall, reedy grasses, and certainly no trees.
So a true links course is not any course that is treeless. The term "links" historically applies specifically to strips of land in seaside areas that feature sandy soil, dunes and undulating topography, and where the land is not conducive to cultivated vegetation or trees.
Because they were built on narrow strips of land, links courses often followed an "out and back" routing. The front nine went out from the clubhouse, one hole stringed after another, until reaching the 9th green, which was the point on the golf course farthest from the clubhouse. The golfers would then turn around on the 10th tee, with the back nine holes leading straight back to the clubhouse.
In modern terms, a "links course" is more broadly defined by Ron Whitten, the great writer on golf course architecture for Golf Digest, to include golf courses build on sandy soil (whether seaside or not) and that are buffeted by winds. Whitten says a links course must play firm and fast, with sometimes crusty fairways and greens that feature many knolls and knobs to create odd bounces and angles. And, of course, a links course, in Whitten's definition, needs to be relatively treeless with a native rough that is tall and thick.