Repetition means repeating. The use of repetition is used very often in design. Patterns are a type of repetition, such as the ones you find on striped shirts.
In Landscape Horticulture, repetition is used to create borders with shrubs or used to break up different areas. The repeated use of a type of plant or other material can create walk ways or designs in the landscape!
Other Horticulture areas such as Floral Design are also known for their use of repetition!
Here are some examples!