Layers in your document can be grouped so that they appear as one layer. You can move and resize them as one and yet you can still go into the group and change the individual layers inside.
Groups in Sketch are a very powerful tool. Because they are just layers themselves, groups can be grouped, moved and resized as well. If the group contains a text layer it will scale up the fonts too.
You create a group by selecting one or more layers. Then click the Group icon in the toolbar and Sketch will create a new group with those items. You can also drag objects between groups in the layer list as you would expect.
Once you have created a group, you can double-click on it to view and edit its contents. You can move the layers inside the group around and even add more layers. Whenever you click on an object outside the group, Sketch will take you ‘out of’ the group so that you can select other layers in your document again.
If you now click on a layer in the group it will select the entire group instead. In a way this works exactly the same way as shapes with subpaths do.
By default a layer inside a group cannot be selected directly, without first double-clicking the group. If you hold down the ⌘ key however, Sketch will let you select layers nested deeply inside groups directly.
If you only use groups as an organisational component in the layer list and you don’t want to have to double-click all the time, you can also mark a group as being click-through enabled in the inspector And there's even a setting in the global Preferences where you can define this behaviour for new groups.