There are already numerous threads on this subject but here is other info...
https://en.wikipedia.org/wiki/Female_ejaculation
http://www.thefrisky.com/2013-03-27/...out-squirting/
So What Is Squirting?
Squirting, or female ejaculation as it's often called, happens when you expel fluid through your paraurethral ducts which are located near the entrance of your vagina. This fluid is usually clear in color and does not come from your bladder, but instead comes from your Skene's gland. This gland is very similar to the male prostate and the fluid that it generates, that you squirt out, is similar to male prostatic fluid too.
The Skene's gland is located just above your G-spot. As it enlarges, it pushes on your G-spot making it more sensitive and pleasurable to have stimulated.
To make your Skene's gland enlarge, you need to turn yourself on and get aroused. It doesn't happen instantly, so it's best to give yourself at least 20 minutes of getting yourself horny and aroused before attempting to stimulate it. A great way to do this is through reading erotica or even using a vibrator on yourself.
In many ways, the Skene's gland is like a sponge. As you get more and more aroused, it soaks up more and more fluid.