Companion Planting
Plants are great alone but can have different effects thanks to their neighbors. Plants that have positive effects on their neighbors are called Companion Plants. Plants that have a negative effect are Allelopathy Plants.
Different types of benefits of companion plants are:
Deterring Pests
Attracting Pollinators
Shade Regulation; such as when a tall sun-loving plant blocks the sun from a short shade-loving plant
Improved Soil Health
Weed Suppression
One example of Companion Plants are tomatoes and basil. Both are often used in the kitchen, so growing both can be useful. However, basil can be used to repel tomato-loving pests such as thrips and moths.
One example of Allelopathy Plants are beans and garlic. Beans, and other legumes such as peas, should not be planted with garlic as garlic can stunt the pea plant's growth. Garlic should also be avoided by onions as its potent stench can attract onion maggots.
Sources:
https://www.almanac.com/companion-planting-guide-vegetables
https://www.burpee.com/blog/companion-planting-guide_article10888.html
https://www.thespruce.com/what-is-allelopathy
https://www.bobvila.com/slideshow/bad-neighbors-11-plant-pairs-never-to-grow-side-by-side-51113
https://www.homesandgardens.com/gardens/garlic-companion-planting