What's up everyone! I found an iPhone last night at the bar. I'm stoked I found it

My first question is how can I now get to the main screen? The iPhone has a screen that shows the iPhone/iPod USB with an arrow pointing to the iTunes logo and underneath it it says "Slide for Emergency." Is this some sort of block that the person put on their phone that they lost it? When I take the SIM Card out, it tells me to "Insert a valid SIM..." Any and all help is greatly appreciated and welcome! Thank you much!