The Toolbar (also called the Tools Panel) contains all of Photoshop's tools. By default it's located on the left of the screen, but it can also be moved.
It can be either one or two columns wide. Just click on the double chevron at the top, to switch between one and two columns.
Most buttons on the toolbar contain multiple tools. Only one tool is initially visible on each button, until you click and hold, then the other tool buttons become visible. The small triangle in the bottom right corner of a button indicates that there are also other tools sharing the button.
The Tools are listed in the order they appear on the toolbar. The default tool is shown first, but the visible tool will be the last tool used.
