It allows you to make selections in the form of various ovals and circles. By default it is free form ovals but hold shift while you make the selection and it will do a perfect circle.
In photoshop the oval tool is called the ellipse tool. The keyboard shortcut for all the shape tools is U (press the U key). It will highlight the currently selected shape tool in the tool bar on the left of the photoshop window. If the ellipse tool is not allready showing just click the little triangle in the lower right of the shape tool to bring up all the shape tool options, find the ellipse tool and click it. There is also an ellipse (oval) selection tool called the elliptical marquee tool. The keybaord shortcut is M for the marquee tools. To find it use the same method as above.
Using selection tools from Toolbox: Magic Wand, Quick Selection tool, Rectangular and Elliptical Marquee tools...
The Marquee tool is just a way of creating a selection in a certain shape. The rectangular marquee tool creates a selection in the shape of a rectangle (as you might imagine), whereas the elliptical marquee tool creates a selection in the shape of an ellipsis (oval) or circle.
Use any selection tool from Toolbox on left side of screen (Window>Toolbox). Selections tools are Magic Wand (W), Quick Selection tool (W) Rectangular Marquee tool (M), Elliptical Marquee tool (M) or use powerful Color Range command from Select menu.
The elliptical marquee tool is a selection tool in graphic design software that allows users to create elliptical or circular selections on an image. It is commonly used to highlight or modify specific areas of an image by selecting and working within the chosen shape.
The eraser, the marker/pen, the Marquee Tool, and the Type Tool.
The Single Row Marquee Tool.
Photoshop Lightroom does not have such a tool. Anyway you can use external editing software like Photoshop or Photoshop Elements. See related links for more details.
There are four different marquee tools.
For selections you can your the Marquee Tool, Lasso Tool, or Magic Wand Tool. To cut that selection you can use the Move Tool, or the Ctr-X keyboard shortcut.
Shortcut key is M. Tools are grouped in Photoshop, to cycle through tools in marquee selection group press M or Shift + M, depend on what is defined in Edit > Preferences > General - look for Use Shift Key for Tool Switch, when this option is checked you must press Shift + M.
Selections tools inside Adobe Photoshop are : Lasso tools, Marquee tools, Magic Wand and Quick Selection, Color Range from Select menu and you can also trace edges with Pen Tool or Magnetic Pen Tool which is accessible when Freeform Pen Tool is active.