Answer
Object Groups
You can create groups by selecting objects and pressing ctrl/cmd + G
Layer Grouping
Grouping layers is not quite the same as in photoshop. You can stack layers by drag and dropping layers onto an other layer. It can help to organise your file. But unlike in photoshop (with layer styles, effects and masks) illustrator groups and layers don’t have much functionality.
Attribution
Source : Link , Question Author : localhost , Answer Author : Julian Steinmann