The word "counterfeit" refers to the manufacture of goods that are made to resemble those produced by a famous brand with the intent of fraudulently passing them off as the real thing. This allows the counterfeiter to take advantage of the perceived worth of the brand-name item while producing it for less.
The trademark law question primary relates to names and logos. It is common in the apparel industry for certain designs to become fashionable, and other designers to imitate them, and that alone is generally not counterfeiting or trademark infringement. For example, another company could make a black leather bag which looks similar to one made by Prada, but without the logo. The PRADA logo is a famous trademark and including it on a bag made by any company other than Prada (or a licensee of Prada) would be trademark infringement and illegal counterfeiting.
Q: What is the difference between counterfeit goods and counterfeit marks?
A: A counterfeit good is a product that's branded with a trademark not owned by that product's manufacturer. A counterfeit mark is a mark that's used by someone w/o a license from the mark owner.
Q: If I take a copy of a good looking of a bag and manufacure it outside of America, am i infringing trademark law?
A: Intellectual property rights (in your situation, trademarks, trade dress, trade names, and design patents) are all territorial -- which means those rights can only protect a product in a particular country if the product manufacturer (or licensee / dealer / retailer / etc.) seeks and acquires those rights in that country. There are about 194 countries in the world. Many have very expansive (and refined) intellectual property laws. Some have very lax laws, some have none, and -- to bring this down to a practical level -- the various countries' enforcement of their laws runs the gamut from "a whole lotta enforcement" (the US) to "not all all" (Sierra Leone).
The answer to "Can I lawfully make and sell a replica Gucci handbag" depends, therefore, on where in the world you make the sell the handbag.
So ... let's assume that Gucci has a line of handbags but decides not to seek trademark / trade dress etc. protection in Sierra Leone. A person in Sierra Leone may, therefore, lawfully manufacture those exact handbags -- even up to including the Gucci trademark. That person cannot export those bags, however, to any country where Gucci has intellectual property rights in its bags.