Like most photo-editing apps, Phonto allows you to take a photo with the camera or import a photo from your albums. From there, you can type in text and easily position it where you want it. You can move the text around by dragging it, or if you need more precise positioning, there are positional arrows for moving the text slowly into place.
Fonts and styles are where Phonto excels. Text, stroke, and background can be any color or a gradient of up to four colors. There are numerous fonts included in the app but, if you don't see one you like, you can add any TrueType font to the app.
To add a font using only your iPhone or iPad, simply search for TrueType fonts in Safari and download one. When you click a link or button to download the font, you'll have the option to Open in "Phonto". This will give you the option to install the font into Phonto and use it on any future photos. No other app that I know of allows you to find, install, and use any font that you want.