The Sql property represents the SQL query that defines what is shown in the embedded List. Typically, you would only animate this property if you were configuring an embedded List for use in a Group Template and Group Instances or if you were configuring an embedded List that was to be filtered by an animation.
When using an Sql animation, the string has to use the correct syntax. The easiest way to check that the SQL Query part of the animation string is correct is to display the Query tab on the Properties window of the embedded List, then right-click and select the Generate Animation option. This copies the SQL Query used for the embedded List and converts the copy into the correct syntax for the Sql animation property (the converted SQL Query is added to the Sql animation automatically, ready for you to edit it as required).
You can configure a button or another selectable Mimic object to apply different filters to an embedded list. To do this, you will need to animate the Sql property and set up a registry key pick action. For more information, see Using Registry Settings to Apply different Filters to an Embedded List.