What is an editor-in-chief?

When speaking of a periodical publication, there will generally be many different topical sections in each edition. Each different section is a different department within the publication, often with it's own staff and editor. The editor-in-chief checks the work of the other editors and ensures that the work of each department blends to form a smooth final product. Also the e-i-c will give instructions to the editors of each department to ensure that all departments are working on complementary paths from the beginning