To select text, you have the following options:
Hold left mouse button, and drag mouse to highlight text.
Click once on a word to move the cursor to a new area.
Click twice on a word to select the whole word.
Click three times to select the whole sentence.
Holding the left mouse button, and dragging the text you want to select, automatically copies the selected text to the clipboard.
Holding shift and using the arrow keys allows you to select portions of the source code in the editor window.