About going abroad, what's the difference between skilled immigrants and work visas?

Skilled migration: The employing company directly applies for immigration green card for employees. Usually people in high-tech industries. Work visa: the employer first applies to the Ministry of Labor for permission, and then applies to the embassy for a work visa after it is approved. Work visas have a limited number of years, not immigrants. Moreover, not all occupations can get work visas, usually high-tech, economic and artistic.