What is the $175 billion 'Golden Dome' missile shield for US that Trump has unveiled?

What is the $175 billion 'Golden Dome' missile shield for US that Trump has unveiled?

US President Trump has launched a space-based missile defence plan called the Golden Dome, promising protection against threats 'even from space'. With multi-layered interceptors and orbital lasers, this system could reshape global defence — but with a projected cost of a over $500 billion. Is this ambitious plan realistic?