Clipping mask: It is a path that masks any object below it , so only what is inside or below the path is visible. The base layer defines the visible boundaries of the entire group. Clip mask is applied to group of layer. For example, suppose you have a shape in the base layer, a photograph in the layer above it, and text in the topmost layer.by using clip mask, the top layer text mask all the layer below it and the object just below the text is visible.

before clip mask
after clip mask

Clipping set:- clip mask and the objects that are masked . You can make a clipping set from a selection of two or more objects or from all objects in a group or layer. All operations  such as transformations and alignment, are based on the clipping mask’s boundary, not the unmasked boundary. Once clipping mask is done , the clipped content can be selected  by using the Layers panel, the Direct Selection tool.

Make sure that clip path must be on the next layer and at top of the object. Clipping path must be only one whatever be the number of object. If there are more than one object than it should be on the same layer.

Possible Ways to make clip mask

11.      Drop down menu. object> clipping mask > make
22.     Shortcut key : cntrl+7
33.      Layer panel : make /release clipper mask icon
44.      Right click :- highlight all object & select make clipping mask ,Create a mask from a group  of layer


 Add or remove an object from masked artwork

This can be done by drag the object into or out of the group or layer that contains the clipping path in the Layers panel.

Release objects from a clipping mask

Do one of the following:
  •  Select the group of object having clipping mask, choose object>clipping mask> Release.
  • Click the name of the group or  layer that contains the clipping mask. Click the Make/Release Clipping Masks button at the bottom of the panel.
  • Select Release Clipping Mask from the panel menu.