Eraser Tool

The eraser tool is used to clear the pixels in a layer or selection. Wherever the user strokes with the eraser tool the pixels are set to a level of transparency determined by the tool settings. Erasing is the simplest way to place transparency in the selected layer so that the content in the layer or layers below can be seen.

The eraser tool is a destructive editing tool. It permanently changes the image in the layer when it is used. Layer masks, which are non-destructive, can generally be used to perform the same function as the eraser tool with much more fexibility.

The Gifgit online editor eraser has several settings to modify the behaviour of the eraser tool:

Size: Sets the diameter of the eraser brush strokes.

Blur: Set the spread of the brush stroke reducing its hardness.

Opacity: A fully opaque eraser (100%) completely erases the pixels in its stroke. If you continue to decrease the opacity of the eraser to zero the eraser will not affect the image.
Related Links:
Canvas drawing
Canvas drawing techniques
Composite operations in HTML5 canvas