Question

what is the use of pencil and bucket fill tool​

Answer 1

Answer:

Pencil to draw or write.

Bucket fill tool to fill colour.

Answer 2

Answer:

This option makes GIMP fill a pre-existent selection or the whole image. A quicker approach to do the same thing could be to click and drag the foreground, background or pattern color, leaving it onto the selection. This is the default setting: the tool fills the area with a color near the pixel onto you have clicked.