What is imperialism and do forms of it continue today? Why?

Roosevelt and Imperialism

What is imperialism and do forms of it continue today? Why? We are closer to the 20th century, AND we have moments coming to life (sadly).

http://www.theodorerooseveltcenter.org/Learn-About-TR/TR-Encyclopedia/Foreign%20Affairs/Roosevelt%20Corollary
https://history.state.gov/milestones/1899-1913/roosevelt-and-monroe-doctrine
http://www.ushistory.org/us/44e.asp