Explanation:

In SQL, after groups have been established using the GROUP BY clause, predicates are applied in the HAVING clause. The HAVING clause allows for the use of aggregate functions to filter the groups based on specific conditions.

GROUP BY clause:
The GROUP BY clause is used to group rows based on one or more columns. It divides the result set into groups of rows based on the values of the specified column(s). This is typically used with aggregate functions such as SUM, COUNT, AVG, etc. to perform calculations on each group.

HAVING clause:
The HAVING clause is used to filter the groups created by the GROUP BY clause based on specific conditions. It is similar to the WHERE clause, but it operates on groups rather than individual rows. The HAVING clause can be used with aggregate functions to specify conditions that the groups must meet.

Example:
Consider the following table named "Sales":

| Product | Category | Quantity |
|---------|----------|----------|
| A | X | 10 |
| B | Y | 5 |
| C | X | 15 |
| A | Y | 8 |
| B | X | 12 |

If we want to find the total quantity of each category and only display the categories with a total quantity greater than 10, we can use the following SQL query:

```
SELECT Category, SUM(Quantity) as TotalQuantity
FROM Sales
GROUP BY Category
HAVING SUM(Quantity) > 10;
```

The GROUP BY clause groups the rows by the "Category" column, and the SUM(Quantity) calculates the total quantity for each category. The HAVING clause filters the groups and only includes the categories with a total quantity greater than 10.

The result of the above query would be:

| Category | TotalQuantity |
|----------|---------------|
| X | 37 |
| Y | 13 |

In conclusion, after groups have been established using the GROUP BY clause, the HAVING clause is used to apply predicates and filter the groups based on aggregate function calculations.