Final answer:
An alias is an alternative column heading displayed in the output of a query, allowing you to give a temporary name to a column or table.
Step-by-step explanation:
In the output of a query, an alias is an alternative column heading that can be displayed. An alias allows you to give a temporary name to a column or a table in the query, making the output more readable and meaningful.
For example, let's say you have a table called products with columns like product_id, product_name, price. In a query, you can use an alias to replace the column names with more descriptive headings like Product ID, Product Name, Price, etc.
The usage of aliases not only improves the readability of the output but also allows you to perform operations on the columns using the alias name.