The Marquee Tool
The Marquee tool is the most basic of selection tools and often the one most useful. This tool is used to draw selections based on geometric shapes. Specifically, the marquee tool allows you to draw rectangular and elliptical selections. To form the selection, simply click and drag the mouse. 
The options bar
The options bar is used to choose settings for each tool for example opacity, fade distance, blending mode. Options on the bar change depending on which tool is currently chosen, and your choices will remain in effect until you change them.
Layers in photoshop
To create a layer and specify a name and options, choose Layer > New > Layer, or choose New Layer from the Layers panel menu. Layers are so important in photoshop because it makes it much easier to edit your work without destroying other parts of your work in the process. it is also important to name the layers in your photoshop work so you now which layer is which and to speed the design process of your work up.
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