A dildo is a fake penis. For centuries girls and women have used dildos to pleasure themselves, as can be see on old Greek pottery.
Some women like the fullness of penetration when masturbating, sliding the dildo in and out the vagina.
Dildos can also be used for anal penetration by both girls and guys. When you want the dildo to stay in the anus you can use a butt plug.
In the past they were made of ivory, wood or jade. Nowadays most are made of plastic, silicone, jelly (PolyVinylChloride), cyberskin (PVC + silicone), latex or rubber.
To avoid STD’s use only your own dildo or cover it with a condom. When you go from the anus to the vagina use and change condoms between insertions to avoid vaginal infection.

Different kind of dildo’s
How to use a dildo?

What is the difference between a dildo and a vibrator?
Is it dangerous to use a dildo? The first time I used it I lost some blood.

See also: strap-on dildo