In the diagram, which state is the start state?
The automaton is always in one of the finite number of states. This state is called the current state of the automaton. Think of a game token that indicates the current state. As the current state changes, the game token moves between states along the arrows.
The automaton always starts in the start state. In the diagram, this means the game token always starts in the start state (as shown above).
The input string is a string of characters examined by the automaton. This string is examined one character at a time starting with the first character. The current character is the character currently being examined.
If there is a transition out of the current state that is labeled with the current character, then the current state changes to the state at the end of the transition and the next character in the string now becomes the current character. The game token moves along the arrow labeled with the current character.
Is there a transition out of the current state (in the diagram) that corresponds to the current character?
If so, mentally move the game token to the new state and change the current character.