When the sentence is talking about a metal object, it's referring to a way of shaping the metal, for things like making jewellery (and hundreds of years ago it would have likely been about making swords and other weapons) by striking or compressing it in some way with a lot of force - basically beating it into a different shape. If it's talking about "forging a friendship", then it means to make a new friend - or, literally, to create a friendship. If you want more, try en.wikipedia.org/wiki/Forging.

Salaam. Forge does mean imitate, often used in the noun or adjective sense: "this is a forgery!" or "this is a forged check!" The root meaning "forge" to make things out of metal, usually by hammering them. A "blacksmith" (metal worker) works at a "forge" (a place where things are made from metal). forging is also used metaphorically in a few senses. it probably originates from the original meaning of making things using metal. example: "Forging a friendship" means crafting a solid friendship over time. also, "Forging ahead (down the road)" means to continue on in making progress in your trip. both of these uses are not extremely common, but also not rare (every native speaker would know these, but not use them often)

I think Ian's explained it pretty well. :) I checked the etymology. Both meanings of "forged" come from a Latin word meaning "make/build/construct", BUT at one point in history, the meaning of "forged"=imitation diverged slightly from the original word, via an old French verb "forgier"=to falsify. The metalworking definition of "forged"=made in a forge(workshop) didn't diverge much from the original Latin word. And now... we have the same word suggesting two rather different things.