Yakisoba in traditional Japanese cuisine is noodles (“soba”), fried (“yaki”). Noodles varies but you can use ramen, udon, or others, and it’s stir fried up with vegetables, meats and a worcestershire based sauce and has been in japan since the 1930’s so like most things it means different things in different places.

This is my personal gold standard for yakisoba: https://sanyofoodsamerica.com/products/sapporo-ichiban-chow-...

But I’ve also seen “yakisoba” served up in US military mess halls and correctional institutions as little more than spaghetti noodles and hamburger as well.