Value describes the the relative lightness or darkness of a color as well as shades of gray.
Texture describes the surface of an object or element, grainy, rough, smooth and flat etc.
Value is very important to any type of design. When the value of the back ground and text are to close, it makes it difficult for the viewer to read. Images look better on some backgrounds rather than others depending upon the values as well as colors in the image. It is fun and adds variety to a design to use different colors and values. Contrast is important to any image you want to be seen by your viewer.