Photoshop blend modes are a very important tool in Photoshop CC 2018. As a beginner, you should be familiar with what blend modes can do for your image.
There are five group of blend modes and in each group, you will find several options.
The idea is that they blend two images together. The either darken your image, lighten your image or a combination of the two.
A really cool trick is to use Shift and plus or minute sign to go through them quickly and see their effect live.
Video by Howfinity