I'm reading the O'Reilly Book: LDAP System Administration.

I'm a little confused about what they call an "attribute" and what they call an "attribute type."

For example: are dc and ou attributes? Or something else?

Are attibute names to the left of the '=' or the left of the ":" or either?

For example, consider:

# LDIF listing for dn: ou=devices,dc=plainjoe,dc=org
dn: ou=devices,dc=plainjoe,dc=org
objectclass: organizationalUnit
ou: devices

Is "dn" an attibute?
Is "ou=devices" a attribute's value, or an attribute?
Is "objectclass" an attribute?
"ou" seems to be defined twice. In the top, after "dn:" ou is defined like "ou=devices". Then later, ou is defined like "ou: devices"

I know it seems like such a small thing, but it bugs me and makes it hard for me to go on without knowing what's what.

//unrelated to networking. moved to Linux - General

Yes they are, or precisely they are attribute names.
Names are to the left of the delimiter, whatever it is.
No, it's the distinguished name, something that uniquely defines the directory entry.
Neither, it's an attribute name followed by its value.
It's an attribute name."ou" isn't defined in the dn, it just has been chosen to build the dn.