There are many symbols used in schematics and diagrams (same thing) to establish what an individual component is.

For example, below are the common symbols found in a DC circuit.


In this pic, V1 is commonly known as a DC power source (for ex, battery).
The wider bar resembles a positive terminal, while the shorter bar is negative.

The negative terminal is wired (red line) to the ground. Ground is usually 0V, but this can vary in AC circuits, or even in DC when ground is used as reference voltage in more elaborate circuits. Do not always assume that ground will be 0V!
Oh yeah, and it's the symbol that looks like a bunch of horizontal bars forming a triangle that points down.

To the right is the VCC (5V) which usually means the power rail. Power rails are usually directly connected to a power source. It just looks a lot neater using VCC in a large circuit, rather than drawing the actual power wires everywhere. VCC stands for Voltage Collector Current (i have also seen Voltage Common Collector). I will discuss collector current later in transistors/digital parts. The name also used due to popularity it has dealing with semiconductor-type devices.