Using Gimp: The Select Tools
The select tools are used to define enclosed areas of the active layer so they can be manipulated without the unselected regions being changed. There are two types of tools:-
1. Tools which you Manually define the area. These are Rectangle, Ellipse and Free Select Tools.
2. Tools which have some intelligence and help predict the area required. The Fuzzy Select and Colour Select Tools use the colour of the region for selection while the Scissor Select Tool tries to follow the boundary between two dissimilar regions.
For help with the Scissor Tool see my video Blurring the Background using the Scissor Tool.
The Manual Select Tools
The Colour Select Tools