Nature of Trust Relationship in Active Directory..

What is trust relationship in active directory ? Full Video in Tamil..
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A trust relationship exists between only two domains. Each trust relationship has just one trusting domain and just one trusted domain. A two-way trust relationship between domains is simply the existence of two one-way trusts in opposite directions between the domains.
Trust relationships are an administration and communication link between two domains. A trust relationship between two domains enables user accounts and global groups to be used in a domain other than the domain where the accounts are defined.