There are three types of lake access for the lakes in Northern Wisconsin. They are private, semi-public, and public. A private lake is a lake that has no public access points and is surrounded by private land. It is very common for a lake lot in Northern Wisconsin to be advertised as "private" when the lake is in no way private. Private lakes are very, very rare and if you see a lake lot advertised as private, make sure to follow up with questions on access. A semi-public lake is fairly close to a private lake. There are currently no public access points. A semi-public lake can become a public lake at a later date, whereas a private lake cannot. Semi-public lakes are generally smaller lakes away from the major cities. A public lake is a lake with easy to get to public access points. Most lakes in Northern Wisconsin are public lakes.
There are many reasons why lake access type is an important factor in assessing a lake lot. The first reason lake access is important is that it determines how busy a lake will be. A public lake will have people fishing and boating on it for pretty much all hours of sun light. Northern Wisconsin is a vacation destination that people are attracted to because of the lake activities. Everyone without their own lake lot heads to popular public lakes (usually lakes on chains or really large public lakes) to do their boating and fishing. This means more people, more people means more noise and activity to deal with than a semi-public or private lake. Some people prefer the noise and activity, some prefer the quiet and there is no right or wrong answer. Just be aware that a "Private Lake Lot" on a public lake is not private at all, even if there doesn't happen to be boats racing around while you are on the lot. A semi-public lake is basically a public lake that is off the beaten bath which greatly reduces its usage compared to a public lake with easy access. It is typically far, far more quiet than a public lake, but is less private than a private lake. A private lake will almost always be quiet. People who buy on private lakes are typically looking for peace and quiet and their lake use is more tempered than those who live on public bodies of water.
The second reason lake access is important is the "feel" of the lake. A feeling is difficult to put into words but I will try to do my best. For this illustration, I am going to compare owning a lake lot in Northern Wisconsin to a family outing at a water park. When owning on a public lake it feels like you took the family to the waterpark for the day of fun. There is always stuff to watch and take part in, but in the sea of people, you are just another one of the dots. Everything you do will be seen, but it will be seen by people you probably have never seen before and will probably never see again. You can still spend quality time with your family, but it is in the public view. A lake lot on a semi-public lake is like going to the water park on a corporate outing. You know more of the people that are out and about on the lake, but not everyone. A lake lot on a private lake is like going to the water park on a day where a group of people you know rented the whole park for the day. You still do the same things you would have if a bunch of strangers were there, but it is far less crowded and you are at least vaguely familiar with everyone you bump into. It is also more private and safer when there are no strangers on your lake. Having spent a lot of time on a private lake, I can assure you that there is a feeling of being part of a community with common interests that isn't available on the other types of lakes.
The final reason lake access is important is restrictions/protections. Public lakes are public lakes with public rules. Private lakes often come with protective convenants. Things like boating hours, fishing regulations, and architectural styles are often covered by protective covenants. When looking at a lot on a private lake, it is important to ask what sort of additional protections have been put on the lake. If you want to ride your jet ski until sunset every day or just don't like being restricted by rules of any sort, a private lake with "quiet hours" in the evening would not be for you.