Characteristics of a Modern Style
Clean Lines And Minimal Decor
Preceding modern design, there were Gothic, Renaissance, and Victorian styles, incorporating heavy textures, ornamentation, and plenty of dark and dramatic elements.
Modern design rejected these, in favor of clean, straight lines, uncluttered spaces, and an overall lack of fussiness.
Open-Concept Floor Plans
Basically, you want as few walls as possible. Furniture, instead, should differentiate spaces, like a kitchen counter providing a visual distinction from a living or dining room.