This was something, not very long ago, was understood as something women recovering from cancer or vaginismus do.
Chemotherapy and other cancer treatments can intensely damage mucuous membranes in the vagina, drying it out and causing irritation and scarring. It can inflame and thin vaginal walls. It can also lead to increased UTIs. Any (actual) woman and most men here can understand how painful that would be from reading it.
Dilation is the use of tools that start small and increase in size that a woman inserts in herself in her own time and "adjusts" to. It's recommended to help maintain tissue flexibility and to prevent scar tissue from the cancer treatments, easing pain over time and enabling some healing which helps for future paps, pelvic exams, sex, and tampon insertion,
In women with vaginismus, where pelvic floor muscles "close" involuntarily (for often mental, but sometimes just plain physical, reasons), dilation can be a way to help prepare them for pelvic exams, pap smears, sex, and tampons. This is a notably frustrating condition for women, especially those in relationships or needing specific health care.
These days... some men who are so horny, groomed, and/or brain broken that they decide to LARP as what they think women are, dismiss the above and decide dilating is just a little TRANSGIRL thing where you have to put dilators, but also sometimes dildos because Horny and Sexualize Everything, into their self-induced crotch wound forever so it doesn't close shut because it is a medical abomination not meant to exist. Imagine you have a wound on your arm and the doctor, instead of cleaning and bandaging it up to heal, is paid a lot of money to instead instruct you to keep putting a plastic stick inside it to keep it open while it scabs over and tries to heal itself shut but can't. Then they sexualize the language around it and eventually the whole concept, and overrun information about it while erasing actual womens' struggles and non-voluntary medical issues.
Voila!
