Along the left side of Photoshop interface, there is toolbox which contains all tools that can be use along designing process, as well as several other functions. The tool is separated into few categories such as Selection Tools, Alteration Tools & Drawing Tools.
Toolbox Overview 5

Toolbox Overview

Revealing the hidden tool

A -Toolbox
B -Active tool
C -Hidden tools
D -Tool name
E -Tool shortcut
F -Hidden tool triangle

There are several tools hidden in a same category. To reveal the tools, right click and select the right tool like figure above.