It all depends on where you’re going to use your logo. If you only need it for your website or other online use such as social media, a smaller resolution (such as 72dpi) will work great and a PNG logo might be all you need. If you need a transparent logo, you’ll be glad to know the PNG format supports transparency. If you’re planning on using your logo in print, a hi-res (300dpi and up) PDF logo could work, but you might need a scalable vector logo format – that’s why it’s always a good idea to get an SVG logo as well. If you need an editable file that you or a graphic designer can make changes to later, be sure to get a logo PSD or AI. As for your logo’s aspect ratio – again, it all depends on your plans for your logo. A square ratio will give you the most flexibility, while a horizontal logo will still be pretty easy to fit in website headers, social media cover images, and more. A vertical logo might be harder to work with.