In eminent domain procedings a governmental unit is able to essentially take private property for a public purpose but must pay a fair value as determined in the procedings, but often less than the property owner had asked. Trump has essentially partnered with government agencies to take land when he's been unable to acquire the land directly from the property owner. The town takes the property through eminent domain and Trump then buys the land from the government.
Trump has also supported Kelo, the US Supreme Court decision that ruled in favor of eminent domain where property is taken for purposes of economic develoment and transferred to private developers.
NEXT: Trump's Faith
(1) Ilya Somin, "Donald Trump's history of eminent domain abuse, " The Washington Post, August 19, 2015, https://www.washingtonpost.com/news/volokh-conspiracy/wp/2015/08/19/donald-trumps-abuse-of-eminent-domain/?postshare=3571444835737101
(2) David Boaz, "Donald Trump's eminent domain abuse almost cost a widow her house," The Guardian, August 19, 2015, http://www.theguardian.com/commentisfree/2015/aug/19/donald-trumps-eminent-domain-nearly-cost-widow-house