Speech Disorders:
A speech disorder refers to a problem with the actual production of sounds
Speech disorders include:

• Articulation disorders: difficulties producing sounds in syllables or saying words incorrectly to the point that listeners can't understand what's being said.
• Fluency disorders: problems such as stuttering, in which the flow of speech is interrupted by abnormal stoppages, repetitions (st-st-stuttering), or prolonging sounds and syllables (ssssstuttering).
• Resonance or voice disorders: problems with the pitch, volume, or quality of the voice that distract listeners from what's being said. These types of disorders may also cause pain or discomfort for a child when speaking.
• Dysphagia/oral feeding disorders: these include difficulties with drooling, eating, and swallowing.

Language Disorders:
A language disorder refers to a difficulty understanding or putting words together to communicate ideas.
Language disorders can be either receptive or expressive:

• Receptive disorders: difficulties understanding or processing language.
• Expressive disorders: difficulty putting words together, limited vocabulary, or inability to use language in a socially appropriate way.

When Is Therapy Needed?
Kids might need speech-language therapy for a variety of reasons, including:

• hearing impairments
  
• cognitive (intellectual, thinking) or other developmental delays
• weak oral muscles
• excessive drooling
• chronic hoarseness
• birth defects such as cleft lip or cleft palate
• autism
• motor planning problems
• respiratory problems (breathing disorders)
• feeding and swallowing disorders
• traumatic brain injury

Speech-language therapy is the treatment for most kids with speech and/or language disorders. 

Source: http://kidshealth.org/