Speaking is an act dependent on thought and timed execution of airflow and oral motor / oral placement of the lips, tongue, and jaw that can be disrupted by weakness in oral musculature (dysarthria) or an inability to execute the motor movements needed for specific speech sound production (apraxia of speech or developmental verbal dyspraxia).
Such deficits can be related to pathology of the nervous system (central and /or peripheral systems involved in motor planning) that affect the timing of respiration, phonation, prosody, and articulation in isolation or in conjunction.
Dysarthria is the reduced ability to motor plan volitional movements needed for speech production as the result of weakness/paresis and/or paralysis of the musculature of the oral mechanism needed for respiration, phonation, resonance, articulation, and/or prosody.
Both are the inability to plan volitional motor movements for speech production in the absence of muscular weakness.
Apraxia is not a result of sensory problems, or physical issues with the articulatory structures themselves, simply the way the brain plans to move them.