The button with an image of a pencil in it is the "Free-Form Line" tool. It allows you to draw lines by clicking and dragging your computer mouse.
The button with the image of an eyedropper is the "Pick Color" tool. This allows you select an object whose color you want to copy and use the color elsewhere in the image.
The "Text" tool is next to the image of the paint can, and has the letter "T" on it. Use this to type text directly onto your picture.