Selection Tools

Rectangular Marquee - select rectangular areas in an image.
Elliptical Marquee - select circular or elliptical regions.
Lasso Tool - create selections using freehand drawing.
Polygon Lasso Tool - creates straight edged polygonal selections by clicking from point to point.

Background Removal

Background Eraser Tool - erases by using a color difference threshold.
Magic Eraser Tool - works like the paint bucket tool but erases where it fills.