‘Detention‘ means goods are temporarily detained by officers to check whether there is any violation of law. If there is any violation, goods are seized. Otherwise, goods are released. There is no documentary formality involved.
‘Seizure’ means goods are taken in custody by the department when there is a belief (though no yet proved) that provisions of law are violated. There is no transfer of property to government.
‘Confiscation’ means the goods become property of Government and Government can deal with it as it wants (These can be taken back after payment of redemption money).