If you have ever seen a blacksmith beating on a piece of red hot iron with a hammer, you have seen the simplest type of forging. Striking a piece of hot metal with a hammer is forging, and blacksmiths have been doing this for centuries. As blacksmiths experimented with new techniques, they learned that complex shapes could be created by hammering metal into a die. The die contains the shape of the finished product. This is drop forging.
Manufacturers now use many different techniques to forge metal.
Press forging - instead of forcing hot metal into a die with a hammer blow, it is pressed into the die with hydraulic pressure. Roll forging - The hot metal is pressed between two rollers. Cold forging - For smaller pieces, the metal can be pressed into the die without heating it significantly ahead of time. The reason why manufacturers want you to know that a tool is drop forged is because this tells you something about the strength and durability of the tool. The advantage of forging is that it improves the strength of the metal by aligning and stretching the grain structure.