Question

why lasso tool are used

Answer 1

The Lasso tool is useful for drawing freeform segments of aselection border. Select the Lasso tool , and set feathering and anti-aliasing in the options bar. (See Soften the edges of selections.) To add to, subtract from, or intersect with an existingselection, click the corresponding button in the options bar.

Answer 2

for selecting the border of a drawing area which should run your computer