In 3 sentences:
Rural-urban and peripheral-core region migration are most common, though rural-rural migration occurs in developing nations for reasons like employment, family, and marriage. Migration between urban areas involves step migration up the hierarchy as migrants' knowledge and finances increase, alongside other urban-urban moves for education and jobs. Reasons for relocation can be viewed at macro, meso, and micro scales focusing on socioeconomics, origin/destination factors, and individual circumstances, respectively.