An "if statement" is a fundamental programming concept used to make decisions in code. It allows a program to execute certain actions only when specific conditions are met. For example, if a variable called temperature is above 30 degrees, the program can display a message saying, "It's a hot day." This helps control the flow of the program based on varying inputs. If statements can also include "else" clauses, which define what happens when the condition is not met. For instance, if the temperature is 30 degrees or lower, the program might display, "It's a cool day." This structure helps create dynamic and responsive applications.