Here is my understanding, but I'm not an expert:
Developmental Coordination Disorder (DCD), sometimes called dyspraxia, is a type of Sensory Processing Disorder. It can occur on by itself, or with other sensory issues. It may also be occur in conjunction with other bionuerological
conditions (such as ASD or ADHD).
However, DCD is a recognized diagnosis. It appears in the DSM and ICD. This means that it has a diagnosic code number (314.5) that is recognized by insurance and medical providers. SPD is not a recognized diagnosis and is not in the DSM or ICD. This means that it can be easier to get OT services covered by insurance for DCD than for SPD.
Verbal Dyspraxia of Speech (which seems to go by many different names) can occur as part of DCD or they can each occur seperately. They are both motor planning disorders, so they are related. Generally, Verbal Dyspraxia of Speech involves oral-motor problems, while DCD is more global, involving gross and fine motor skills. Some kids with DCD also have oral-motor issues, while others do not. Some kids have only oral-motor problems, but no gross or fine motor issues, so these children would have verbal dyspraxia but not DCD.
My own experience:
My son has dyspraxia (DCD) as part of his autism. He has other sensory issues as well, mainly sensory-seeking. As a dyspraxic sensory seeker, he craves intense movement but is very clumsy at it - in other words, he is very accident-prone. He also has oral-motor planning difficulties, which caused feeding issues (as an infant and toddler), speech problems, and problems with other oral tasks, such as blowing bubbles, making faces, blowing horns, etc. He gets Speech and OT services.
I hope that helps.