Language develops in the process of dyadic, dynamic interactions involving the child, and facilitated by an innate motivation to develop self concept and to socially interact.
Important here obviously is the need for quality time for children with their parents (caretakers).
Parents contribute greatly to language development by modifying their speech output to be more compatible with the child's developing linguistic and cognitive abilities (motherese).
They also take steps to provide a scaffold to facilitate communication.
A scaffold is a consistent pattern of environmental cues, (such as a bedtime routine) in which familiar phrases are used.
This helps children, who have limited communication skills to decode and encode messages.