What Are These?

I use Chrome on my desktop. In my hotmail emails I see these odd little symbols.

 

Basically, it means you have Hotmails security enhanced to not download any possible unsafe content i.e Images etc.
You should be able to 'right click' the icons and select 'download content' if you trust the sender and wish to view this content.

 

Spammers can use embedded images to see if an email has been opened. Most webmail providers and standalone email programs block images by default to prevent this.