What is this music notation symbol?

Hi,

Can someone tell me what the '\' through the staff line after the two notes in the attached image are called and what they mean to do? I tried searching, but wasn't finding anything. My brother who plays piano and knows a little more about music notation also didn't know what it was which I'm guessing means it has something to do with stringed instruments? Thanks.

that denotes a slide down the neck

It's like a glissando.

A downward slide with no specific target.