In searching for help for your penetration problem, you may have come across both the terms vaginismus and genito-pelvic pain/penetration disorder (GPPPD).
The medical field is constantly in flux and changes in naming and classifying conditions occur periodically, including in the field of sexual dysfunction. As of 2013, the most recent edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5)*, no longer includes a specific definition for vaginismus. In fact, vaginismus does not appear at all. Instead vaginismus was combined with another sexual pain disorder, dyspareunia and replaced with new term, genito-pelvic pain/penetration disorder (GPPPD). While GPPPD provides an update on female penetration issues (there had not been one in many decades), lumping female sexual pain problems together is problematic. This lack of specificity complicates both diagnosis and treatment protocols and importantly the way we talk about these issues. One could say vaginismus is a sub-set or type of GPPPD (although it does not state this in the DSM-5).
It is helpful to be familiar with both terms - vaginismus and GPPPD in educating yourself about your condition. Change filters slowly both inside and outside of medical and academic communities and thus it is common for older terms to persevere. Vaginismus will likely continue to be used when referring to penetration problems both over the Internet and by health professionals for many more years.
*The DSM-5 is the primary diagnostic guide used by the health/medical/academic communities for the classification of disorders.