You know cologne is for men and perfume for women but why-what is the difference?

There are colognes for women too.

The difference is all in the dilution. (Well...and the scent. Men wouldn't wear Chanel No. 5 or Shalimar, and women don't want to smell like English Leather.)

The very strongest fragrance product is perfume oil. It's not usually sold to consumers because it's too strong to wear.

The strongest grade you'll find in a perfume store is Eau de Parfum, or "perfume."

Next is Eau de Toilette, or "toilet water." Both of those are made only in scents for women.

Then comes Eau de Cologne, or "cologne." This is made for both men and women, in different scents.

And finally come "splashes" and "aftershaves." These are very faint scents.