Integer overflow occurs when a calculation produces a number that exceeds the maximum limit that can be stored in a variable of a specific data type. For example, in many programming languages, an 8-bit integer can only hold values from -128 to 127. If a calculation results in a number greater than 127, it wraps around to the minimum value, causing unexpected results. This issue can lead to bugs and vulnerabilities in software, as the program may behave unpredictably. Developers often use larger data types or implement checks to prevent integer overflow and ensure that calculations remain within safe limits.