By studying a topic as a whole, the student can dive deeper into their discovery of a topic and make connections between subject areas. This approach also allows a student to see a topic from many different perspectives and possibly explore it in a way they may not have if they were restricted to a singular subject. It can expose them to new and interesting ideas and sometime even help them develop further interests and/or a new appreciation for a subject.
This approach of study also has many benefits when teaching children of varying ages (like in many homeschooling families) as it can easily be adapted for a variety of ages. It can also be adapted for a variety of learning styles. Whether the child is a visual, auditory or kinetic learner the topic can be explored as such. Every child is so unique with their own way of approaching learning, a Unit Study approach allows them the freedom to 'tackle' a topic as they would like (draw, read, research, write, hands on, etc).
There is a wide range of 'teaching' methods within a Unit Study approach. Some take a child led, self directed approach allowing their child to explore their topic of interest and let it lead where it will lead. Where others may choose to teach Unit Studies in a more traditional way with a curriculum and ensuring that all or specific subjects get touched. And of course there is everything in between. Like most learning, no two homes look the same.