What does mann mean by property and labor in different classes are essentially antagonistic buy property and labor in the same class are essentially fraternal?

It means that, in different classes, what for someone in one class is labor or work because he or she is doing those duties, for someone in another class that can be his or her poperty because he or she is the employer and owns the resources or products that other people are working on. And when it comes to express the idea in the same class, it means that no matter what is the position of every person, they treat each other as family and they trust each other, something that, if we were talikng about the matters of poperty and labor in different classes, it would not being happening.