Product attributes: what's the effect of scope options

Question

Comparing product attributes in two magento installs, I see that some attributes have a global scope in install 1, and store view scope in install 2. I haven't created these attributes myself, and I don't know if there was a special reason to do this.

Now I wonder what the effect is of this setting.

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Edit: at first I wrote "system scope" instead of "global scope", because it was translated like that for my language.

Answer 1

Default attribute set contains all of the system Attributes that are required for each Product

The orange circles mark the System Attributes. Recall that every set must contain all of the System Attributes because each Product must have all of the System Attributes applied to it.

You cannot delete a Group that has System Attributes in it.

Update

If you are talking about attribute scopes than this manual should help.