When you define a feature layer, you specify the geometric type (point, line, area, text, or multipatch) and the query that uniquely identifies which CAD entities belong to the feature layer.
In the case of a web feature layer, it is always Layer = ESRI_<name of feature layer>.
For document feature layers, you can use Layer = * to include all entities that match the geometric constraint.
The most common use is to specify Layer = <one or more CAD layers> to cover all the entities that are associated with one or more AutoCAD layers.
When working with layer queries, you can use the wildcard characters * or ?’. For example, Layer=ROAD_* would include Road_Centerline and Road_Curbline.
In the user interface, you can define queries based on color, layer, line type, and line width. However, if you know the AutoCAD DXF codes, you can define more complex queries such as all the block inserts on a specific layer using the DXF code 0 and theINSERT value. Refer to the Autodesk documentation regarding DXF entity codes for more information on the types of codes you can use in your queries.