SanitaryNapkin
A sanitary napkin, Maxi pad (brand name), menstrual pad or period pad, is an absorbent roughly rectangular thing placed in your underwear? (panties) to absorb menstrual fluid? during menstruation. It's made of a highly absorbent fabric.
They come in different shapes and sizes. The also come in different thicknesses to absorb different amounts of menstrual fluid.
Don't wear one all the time, like if you think you might get your period. When you're having your period, you should change your sanitary napkin once ever 2-3 or 3-4 hours, more if you have a heavy flow. The napkins are thrown out into a sanitary bin or just a garbage if one of those isn't available. You can use the wrapper for the new pad to wrap up the old pad before throwing it out.
My mom says that just because a brand is advertised a lot on television doesn't mean that it's actually a higher quality pad.
Believe it or not this was a very significant invention. In Victorian times women used a washable cloth rectangle sometimes filled with absorbent moss. The disposable sanitary napkin was invented around 1880.
You can get reusable cloth ones made of absorbent fabrics and secured with snaps on wings that wrap around the underwear crotch.
In some places, like India, menstruation is still taboo and women can't talk about how they can't afford sanitary napkins and have to sit on rags. Last I heard some guy was working on making them a lot cheaper.
I recommend reading the WikiHow article linked to below to learn how to use a sanitary napkin (pad)! It's much better than this article.
Many women opt for using a tampon instead of a pad, or even a menstrual cup.