1.The Pen tool is probably the most powerful tool in Adobe Illustrator. It allows the artist to create shapes with freeform curves, and with time and skill, most curves found in the “real world” can be duplicated using the Pen tool. ... It does not draw wherever you drag, like the Paintbrush or Pencil tools.
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2.A brush tool is one of the basic tools found in graphic design and editing applications. It is a part of the painting tool set which may also include pencil tools, pen tools, fill color and many others. It allows the user to paint on a picture or photograph with the selected color.
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3.The Eraser tool changes pixels to either the background color or to transparent. If you're working on a background or in a layer with transparency locked, the pixels change to the background color; otherwise, the pixels are erased to transparency.
