Difference between ldap searches

[radiatejava]

I am trying to understand the difference between these 2 ldap
searches, can anyone explain ?

ldapsearch --hostname localhost --baseDN "ou=Groups,dc=example,dc=com"
"(objectclass=*)" @groupOfUniqueNames

ldapsearch --hostname localhost --baseDN "ou=Groups,dc=example,dc=com"
"(objectclass=groupOfUniqueNames)"

What do we primarily mean by using @<objectclass> format ?

Thanks