Grouping and ungrouping objects

How can I group and ungroup objects? By linking (child-parent)?

You can parent objects by first selecting the child objects and then selecting the parent object as the last object. Then you need to hit Ctrl-P to make the last object the parent.

When you move the parent object, the child objects and their childs etc. will move too. If you move a child object, its parent won’t move.

<edit>fixed a typo</edit>

I understand, but something like group objects? Join objects?

It is possible to join meshes by selecting the the meshes that you want to join. After that you hit Ctrl-j to join them.

AFAIK there’s no group/ungroup function in Blender if you don’t count the parenting option.

yes, to join, you select 2 objects and hit ctrl+J.

there is a way to un-join them (separate)

you select the 2 joined objects, go into edit mode, select the vertexes you want to unjoin, and hit just P

itll bring up a drop down menu and ask you what you want to separate.

an easy way to select the vertexes is by clicking on 1 of them that you want that is on the object, and hitting L. it will select all vertexes connected to the 1 selected

You can group objects in object mode but i’m not sure what use it is.
Parenting is much more useful and does the same basic job.
Joining meshes is even better and the meshes don’t need to be touching either.

Groups are how the particle system (dupliGroup) finds geometry for distribution. It is also a great way to represent a complex object, such as a character with a single empty.

EXAMPLE: Group a bunch of objects together and call them “Group”. Then create an empty, activate dupliGroup and type in the name of your group. The empty will represent all the object in the group as a single object. It is not the parent of the group, however.

Groups are also useful in scripting to detect certain objects sets.