woocommerce – what is the difference between the shipping methods of an area when an order is created with woo api

Please help, when i decide to create an order, i found that i have to specific shipping_lines

"shipping lines": [
"method_id": "flat_rate",
"method_title": "Flat Rate",
"total": 10

that method_id and method_title request so when I get all shipping methods by zone ID, I found methods with the same method_id and method_title
shipping method have the same value id

My question is how does wp make the difference between shipping methods when I place an order.