Chamomile [camomile] plants resemble daisies. There are two plants commonly known as chamomile and they are not the same plant.
Roman and German Chamomile.
The Roman is sometimes referred to as English or Russian Chamomile.
Both species are used for a number of medicinal purposes such as gastrointestinal disorder, muscle spasms, menstrual problems, ulcers and even insomnia. Chamomile oil is documented as an antiseptic and anti-inflammatory agent. 
In the gardening realm it is frequently grown in "tea-gardens" or paired up with up other plants for its qualities as a companion plant. Chamomile enhances the flavor of onions and other aromatic plants and deters some pests that feed on Cabbage family plants. 
It has been documented to have an effect on oil production in neighboring plants. The mechanism behind this is not fully understood but the effect derived from it is real. In some cases this is good - in others it is not so good. In Onions and Alliums - Good, Mint - Not so Good
Chamomile planted near mint will inhibit the mint plants ability to produce the oils that create the mint aroma, it does no harm to the Chamomile plants.
Grown near peppermint, the peppermint produces less oils but the chamomile grows better.
At times you will see Chamomile suggested as a companion for Mint- while they do have some beneficial aspects to their interactive relationship - there are also negative aspects - it is up to the gardener to weigh the pros and cons.
Chamomile does not fare well with carrots or related plants such as parsley and parsnip, they have multiple common pests and pathogens that they freely transmit to one another.
Roman chamomile is a perennial, it is ground hugging plant that gets about a foot high and makes a nice ground cover. German chamomile is an annual shrub that grows 2 to 3 feet tall.
Both varieties produce similar flowers that resemble daisies, and have similar uses and attributes. German chamomile is most commonly grown for its blossoms. Roman Chamomile for its companion planting attributes. Both plants work well for their edible blossoms as well as in companion planting, and both are aesthetically pleasing.
Starting from Seed
Chamomile seeds can be directly seeded into the garden or started indoors for transplant. If starting indoors about 4-6 weeks before the last frost date is best.
Start them in trays or peat pots. Unlike many other flowering plants the seed shouldn't be completely buried in the soil as they require some light to sprout. Sprouts that germinate under the soil surface will frequently rot before breaking through to the light source.
Keep them uniformly moist. After sprouting, you may have to thin them to one per pot. They should be kept in a warm sunny location until transplanted outdoors. When transplanting in the ground be sure to observe a hardening off period.
Seedlings of German Chamomile should be spaced about 12 to 16 inches apart. Roman Chamomile can be planted much closer, about 4 to 6 inches apart if you are planting them as a ground cover, slightly more if you desire a different effect.
A well drained location that receives full Sun to Partial shade is fine.
German Chamomile , although it is an annual will easily re-seed itself from season to season with very little help from you so long as let a small percentage of the blossoms go to seed. Roman Chamomile will keep coming back, and will also re-seed under the proper conditions if allowed to go to seed. Whether planting Roman or German Chamomile you should anticipate having a permanent chamomile bed.
Chamomile seeds sown directly into the garden,should be sown in the early spring, after the last frost date. You can also put the seeds out in the Autumn to overwinter, but should expect a much lower germination rate.
Once established Chamomile basically takes care of itself. Fertilizer shouldn't be much of an issue as Both varieties have light fertilizer demands. Watering also shouldn't be an issue - 2 -3 times weekly is fine, especially at bloom-time. Allow the soil to go just about completely dry between watering. Weeding is sometimes necessary, particularly in German Chamomile. Roman Chamomile would also benefit from occasional weeding until it gets established in a plot as the dominant plant.
Chamomile has a tendency to become invasive and spread to areas that it is not welcome, which is one reason some gardeners choose to grow it in containers. German Chamomile needs a pot of at least 12" roman varieties will do with slightly smaller pots - naturally dependent on how many plants you place in each pot.
Pests and Diseases
Chamomile is not very well liked by the insect realm, most - not all - just most insects will avoid it like the plague. This is one reason it is is prized as a companion plant in vegetable gardens. Aphids, mealybug and rarely spider mites can be found feeding on Chamomile but infestations are generally very mild and easily controlled.
Other Herbs and Spices
|Edible Flowers||Indoor Herbs||Rosemary||Thyme|
References and Footnotes
1. Essential Oil: Production for Health Care in Current Scenario
2...Furthermore, many studies have reported a wide variety of companion plants to contain repellent properties against pests of Brassica crops...chamomile (several genera) ..." Companion Planting and Insect Pest Control
Chamomile, dill, elder and Wormwood extracts were shown to exhibit a clear repellent effect - ..Common Herbs as Grain Protectants
"...savory, chamomile, and thyme are ideal planting crops. These three herbs will attract more beneficial insects than any bright, pretty flower will." - Alabama Cooperative Extension.