Microsoft Paint: Tools
Magnifying Glass Tool

The Magnifying Glass, or Zoom tool, can be used to get a closer, more detailed view of an image. This is very useful if you’re working in close with the fine details of a part of an image. When you activate the Magnifying Glass tool, you’ll have an option to select between 1x, 2x, 6x, and 8x magnification. You can click on the part of the image that you want the magnification to center on. This will not affect the actual image in any way, just how it appears on your screen. Once you zoom in, the magnifying glass will automatically switch back to whatever tool you were using before.

Not too much needs to be said that isn't sufficiently demonstrated by the illustration above.  Compare it to the original-sized picture on the Eraser Tool page.  With the Zoom Tool, you can get up close and personal with every pixel in your image!  If you've got a shaky hand, or need to work with tiny details, the Magnifying Glass will soon become your best friend!

Microsoft Paint: Tools
Pencil Tool

The Pencil tool is your basic drawing tool. You can draw in different colors, but other than that there are no other options. The pencil’s stroke is a single pixel wide, which makes it useful for working with fine details, but a poor choice for filling in large areas of the image with color.

You can do simple line drawings with the pencil if you have the coordination to guide the mouse with great care.
Tip:  To draw straight lines, hold down the Shift key as you draw with the pencil.  Your pencil line will be limited to horizontal, vertical, or a 45-degree diagonal.

Microsoft Paint: Tools
Paint Brush Tool

The Paint Brush tool is similar to the pencil, but has more features. It too can be used in different colors, but the shape and size of the Paint Brush can also be changed. You can use square, round, and slanted shaped brushes, of various sizes, selected in the Toolbar Options.

You can use the various paintbrush shapes and sizes to create a variety of effects.  Draw thick freehand lines like you would with the pencil, or fill in color in unbounded areas.

Tip:  If you hold down Shift as you paint with the Paint Brush tool, you can make perfectly straight horizontal or vertical strokes.  However, unlike the Pencil, you cannot do 45 degree angle diagonal lines with this method.