Open a photo:
With Split toning you can make the highlights yellower and the shadows more blueish.
Start with the box next to the highlights. By clicking on the box next to the highlights, you get a screen where you can pick a colour for our hightlights.
Pick a colour that fits your image. Then do the same thing with the shadows. The balance slider helps you to find the best balance between the highlight and the shadows for your image
Before and after (Y)
So split toning gives great results in balancing the colours in the shadows and the highlights. But the big advantage of Apply image is that you can use masks to decide where in the image you'd like to have the effect and, maybe even more importantly: where not. But split toning is a good alternative.
Just have a go, try it out and see what effect you can create in your image.