Companion Planting
Companion Planting is about planting specific plant species in proximity to each other. This can be done for the following reasons:
Shelter
Larger plants can protect smaller plants from wind or too much sun
Support
Some vegetables can be used as physical supports for others
Beneficial Insects
Some plants attract beneficial insects to help fertilization
Soil Improvement
Plants, like legumes, can improve soil conditions for other plants
Decoy Plants
Plants that emit odors which can mask pest attracting plants
For a comprehensive overview of the different companion planting options we refer you to the overview in wikipedia, click here >