A SQL Query is a tool that allows marketers to manipulate and filter data from data extensions using SQL statements. A SQL Query can be used to find customers who have purchased a camping tent or foldout camper in the last week and exclude those who have a 'silver status'. A Filter Definition is a tool that allows marketers to create filters based on attributes or measures from data extensions. A Filter Definition can be used to apply the SQL Query results to the data extension that contains all customer transactions within the last 90 days. A Journey Builder Entry Source is a tool that allows marketers to define the audience for a journey based on data extensions, filters, or events. A Journey Builder Entry Source can be used to select the filtered data extension as the entry source for the campaign.