NV = Network Virtualization, which is NSX
DCV = Data Center Virtualization, which is vSphere
There are no VCA-DCV and VCA-NV any more though - they were retired at the end of 2017, the VCA-DBT is now the only VCA: VMware Certified Associate - Digital Business Transformation Certification Page
VCP certifications are harder - they have a mandatory training requirement, plus you have to pass 2 exams that are at a deeper technical level.
So, there is a VCP for NV, and a VCP for DCV:
Which VCP should you choose to do? That would depend on which technology you know most about, which one you're most interested in, which one you think is more useful in the job market...