What command is used to make Karel move forward one step?

The command used to make Karel move forward one step is "move()". This command is a fundamental part of Karel's programming, clearly indicating that Karel should take one step in the direction it is facing. When executed, Karel will advance to the adjacent space in front of it, assuming there are no obstacles blocking the path.

This command is essential for navigating the environment and performing tasks, making it a core function in Karel’s programming. The simplicity of the command allows programmers to focus on creating more complex behaviors and algorithms without getting bogged down by unnecessary syntax or complexity.

Other options like "step()", "advance()", and "go()" do not correspond to Karel's predefined commands in the standard programming environment, which is why they are not usable for directing Karel's movement.