Row Level Triggers:

These types of triggers are fired for each row which is affected through the triggering statement. For instance, UPDATE statement for multiple rows of a table. In that case, the ROW level triggers are executed for every row which is affected through the UPDATE statement.

Statement Level Triggers:

On behalf of the triggering statement this trigger is fired once regardless of the number of rows in the table in which the triggering statement affects.

Based on the combinations of the above, there are twelve categories of triggers which can be written on a table.