Speech, or articulation, refers to the ability to produce speech sounds required for communication. For example, the sound "th" as in "think" is produced by placing the front of the tongue against your top lip. Speech is a very complex skill which is easy to take for granted.
Some people have difficullties producing speech sounds correctly. Speech sounds may be distorted (eg. a person may have a "slushy /s/" sound) or substituted for other sounds (eg. a child may substitute "tat" for "cat"). Young children make substitution errors as part of normal speech development, however if it is felt that the child's speech is significantly different or more "babyish" than the speech of other children their age, the child should be assessed by a speech-language pathologist. Speech therapy specifically targeting the problem areas can help to improve the child's articulation skills.
Emerging evidence suggests that there is an important relationship between speech difficulties and literacy difficulties, with children who experience articulation difficulties being more likely to experience difficulties with reading and spellng. While not all children with articulation difficulties will develop literacy problems, evaluation by a speech-language pathologist will help to determine whether your child is at risk. Your speech-language pathologist may also recommend activities designed to strengthen your child's literacy skills.