The Mix Texture node is used for mixing two textures together. By default the Mix Amount is controlled with a float value. A value of 0 means that texture 1 is visible, a value of 1 means texture 2 is visible. Values in between blend the two textures together in a linear fashion. You can also use any texture for the mix amount. The Mix texture is similar to the Cosine Mix texture except for the behavior of the mix slider.
how to use
Open the Node editor and prepare the setup as you see in the picture below. In this setup two textures used for the "mix texture" node and another image texture (which is Octane Logo with alpha) used for the mix amount. If you use alpha image for the amount, only white parts will be used as mask (float value is "1", ie texture 2 is visible). In this case you can see the image assigned to the "texture 2" slot in the Octane logo. This method applies to all mix operations. If you do not use any texture for the amount, then the float value begins to work and mixes the textures between 0 and 1. It is a very useful Node and you will probably use it a lot during texture creation.