A symbol table is a data structure used in programming languages and compilers to store information about variables, functions, and other identifiers. It acts like a dictionary, mapping names to their attributes, such as data types, scopes, and memory locations. This helps the compiler or interpreter quickly access and manage these identifiers during the compilation or execution process. Symbol tables are essential for tasks like syntax checking and semantic analysis. They enable the detection of errors, such as undefined variables or type mismatches, by keeping track of the identifiers' properties throughout the program's lifecycle. This ensures that the code is valid and can be executed correctly.