移民 (yí mín) specifically refers to people moving to a new country or region to settle permanently — it means 'immigrate/emigrate' and also the noun 'immigrant/emigrant'. In contrast, 迁徙 (qiān xǐ) and 迁移 (qiān yí) are broader: 迁徙 often describes animals migrating or people relocating, while 迁移 can also apply to data or systems. 移动 (yí dòng) simply means 'move/shift' without the sense of relocation.