I have iphone se 2nd gen. What is the button on left side above up and down volume buttons?

terue wrote:

What is the button for on the left side above up and down volume buttons?

Ring-silent; the mute switch.

Click on the following blue-text link to more info ➡️ Use the side, Home, and other buttons on your iPhone - Apple Support

Blue text used here in the Apple forums is a clickable link to more information.

That would be the mute switch.

Use the side, Home, and other buttons on your iPhone - Apple Support