A quick guide to the differences between female incontinence pads and feminine hygiene products can be found here
To start, disposable adult liners and pads have many different names. They're also called guards, shields and beltless pads. What they have in common is that they are designed to be worn inside underwear—either regular panties or briefs or incontinence briefs (often reusable ones that last through dozens of washings or more).
Within adult liners and diaper pads specifically designed as incontinence solutions, there are many differences between products, both in terms of the level of absorbency offered (there are pads that may even be sufficient for overnight use) and their shape—it's not just adult diapers that are contoured for men and women, even incontinence pads are shaped with anatomical differences in mind.
Adult incontinence pads made to go inside regular underwear typically have a waterproof backing with adhesive strips to help it stay put. Those designed for incontinence undergarments may slip into a compartment and not have the adhesives.
Virtually all incontinence pads have absorbent layers that draw in liquid and capture it, some with special material such as liquid absorbing polymers that turns into a gel when activated by liquid—urine is trapped and your skin stays dry. A slight loss of urine is often associated with stress incontinence—occurring with activities that exert some stress on the abdomen, like coughing, sneezing, laughing or lifting a heavy object. For this light to moderate level of incontinence, thinner incontinence pads can provide the protection you need. For other conditions that have led to a greater level of incontinence, some adult liners can absorb up to two cups of liquid.
Most beltless pads designed to trap a lot of liquid have gathers on the sides to help contain liquid flow; others have channels designed into the pad to help absorb it. The width and length of the pads differ from brand to brand, often depending on whether they're made for men or women. One more point to keep in mind: The more active you are, the more snugly you'll want your underwear to fit to keep the adult pad from shifting.
Another option is the belted incontinence pad. This design usually has gathers on the sides to help contain liquid flow and an elastic belt that fits around the waist to hold it in place. Some elastic belts come with buttons and others with Velcro. The pad area offers fuller coverage front to back.