An algorithm is a step-by-step procedure or set of rules for solving a specific problem or accomplishing a task within a finite number of steps.
Pseudocode is a simplified programming language that allows programmers to express algorithms without worrying about specific syntax.
A flowchart is a graphical representation of an algorithm using various shapes and arrows to depict the sequence of steps.
Efficiency refers to how well an algorithm utilizes resources such as time and memory. An efficient algorithm completes its task quickly and with minimal resource usage.