Final answer:
A syntax error occurs in Python when the parser encounters incorrect syntax that it cannot understand. These errors prevent the program from executing and typically include issues with punctuation, spelling of keywords, indentation, and matching of parentheses.
Step-by-step explanation:
When the Python parser cannot understand your code, the error that occurs is called a syntax error. Syntax errors are a form of runtime error that happen when Python encounters incorrect syntax within the script. These errors are usually detected before the program is executed. Syntax errors are caused by incorrect use of programming syntax, such as missing parentheses or using an incorrect keyword. For example, if you forget to close a set of parentheses, the parser will throw a syntax error. Common causes of syntax errors include missing punctuation, such as a missing colon or comma, misspelled keywords, incorrect indentation, or unmatched parentheses or braces.