Question about switch and 2 internet lines redundancy

I've got a question about switches and BCP: Switch + 2 incoming internet lines = redundancy and no interruption if one fails?

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Hello

I am early in my IT career. Most of my knowledge and experience is on the software side. I am working on something. I have never worked with a switch. I am trying to decipher their network diagrams. They have 2 incoming internet lines (from the same company though) and they have many different devices. Internet 1 goes to items A B C and Internet 2 goes to items D E F. If Internet 1 goes down, does that mean A B C will automatically jump onto Internet 2, by way of the automated feature of the switch (hence the name, "switch")?