'Greedy states' seek territorial expansion as a result of pressures created by the international system. The anarchic nature of the international system makes states insecure, and greedy states seek to rectify this by any means necessary. 'Security seekers' on the other hand are those already secure in the status quo.

There is no difference, the terms are synonymous.

'Security seeker' states are those interested in achieving security in the international system, whilst 'greedy states' are interested only in amassing power, land, and other resources.

'Greedy' states are those that seek to advance their power through territorial expansion, even when they are already secure in the status quo. 'Security seeker' states are those that only want to be secure in the status quo, although they might get drawn into arms races and war because of structural pressures in the anarchic international system.