In Photoshop it is a small square on the top right side of the photo shop and you can select the colors by making it darker or lighter. Another meaning is adding a color effect in a text or a shape. The effect is like dark to your color. If you want a specific answer you can read this: color gradient (sometimes called a color ramp or color progression) specifies a range of position-dependent colors, usually used to fill a region. For example, many window managers allow the screen background to be specified as a gradient.
It is a part in a gradient where you can change the color of both sides so you can mix the 2 color together in the middle of the object. You can change it by clicking the side bottom icon and change the color then click OK. If you want to remove it you have to drag the black icon up if it is pointing down and down if it is pointing up.
it is when you make the text smoother so you are able to read it. if you want a detailed explanation you can read this:Font rasterization is the process of converting text from a vector description (as found in scalable fonts such as True Type fonts) to a raster or bitmap description. This often involves some anti-aliasing on screen text to make it smoother and easier to read.
It make it more easy for you to work with because it compresses 2 or more layers into 1 icon. It can help you more focused and less confused because if there are many layers it will be hard for you to focus and you would be reading all of the layers and then work which would take time.
The way I do it is hold shift and click on the layers you want to put in the group then you can either do Ctrl g or you can click the group button which is in the bottom right next to the square with a circle in it icon.
The tutorial was 15 min long and it took me the whole block to do it. But I learned how to do it properly and learned how to make groups and gradient color. If you want to see my result it is in the left. Mainly I learned new techniques that i can use in the future in Photoshop.