Final answer:
An alias is an alternative heading for a column in the output of a query, which serves as a temporary, more understandable name in SQL results.
Step-by-step explanation:
A alias is an alternative column heading displayed in the output of a query. When creating SQL queries, you can give a column in the result set a temporary name, which is easier to read and understand than the original column name. This is particularly useful when the names are complex, long, or not very descriptive. For example, if you have a column employee_salary_annual, you can create an alias to display it as simply Salary in the results using the SQL command SELECT employee_salary_annual AS Salary. The aliases are only used within the query's output and do not change the actual column name in the database.