The `!=` (not equal to) or `<>` (not equal to) operator in SQL is a crucial part of data filtering. It allows you to select rows where a specific column's value doesn't match a given value. This operator is essential for querying databases and retrieving only the data you need. For instance, if you want to find all customers who haven't placed an order in the last month, you'd use `!=` or `<>` to compare the order date to a specific date. This operator is often used in conjunction with other comparison operators like `>`, `<`, `>=`, and `<=` to create complex filtering conditions. It's a fundamental building block for constructing queries that extract specific subsets of data from a database table. The choice between `!=` and `<>` is largely a matter of personal preference or database system convention; both achieve the same result.