When do teeth form in children? At what age?
I assume that you are asking at what age kids start having teeth "erupt" -- which is the technical term for when the teeth first start coming through the gums.
If that is what you are asking, most parents can probably tell you that babies start getting their first baby ("primary") teeth when they are around 6 months old. The teeth come in gradually until the child is much older -- there is a broad range of time for getting the full set of baby teeth in.
Please follow the link to see details about which teeth usually erupt at what point.
Deciduous teeth generally follow a pattern in the infant. At about 6-8 months of age central incisors erupt. Followed by the lateral incisors at about 7-12 months. At 16-20 months the canines appear followed by the first molars at about 12-16 months. At 20-30 months the second molars erupt.
Usually, the lower teeth erupt before the corresponding upper teeth. At about the 6th year of life the "six year molars" come in. More changes are seen in the preteen years as well as the teenage years.