Anxiety is a state of heightened emotional arousal containing a feeling of apprehension or dread.
Like fear, the subject feels threatened.
Unlike fear, the subject often perceives the source of the threat in vague or poorly defined terms.
I can give you the example for more understanding.
John is driving his car down a country road.
It is a sunny day and the weather is pleasant.
Abruptly, for no apparent reason, he feels that in some strange way the day is beginning to close in on him.
Very quickly he feels that something awful is about to happen, but he doesn't know what.
It is as if a black cloud of danger is over the car, following him.
His heart begins to pound, his chest feels tight, he begins to tremble, and he feels faint.
He doesn't know if he is about to have a blowout, a collision, a heart attack, or if some other terrible event is about to occur.
He has to pull over to the side of the road, and some times passes before he regains a portion of his composure.
Now I can explain the connection between Freud neurotic anxiety and the example given above fits into a class of anxiety labeled by Freud neurotic anxiety, anxiety caused by mental or emotional conflicts, not objective circumstances.
Without knowing something about John's personal history or life situation we can only speculate as to what triggered his anxiety attack.
However, long-standing doubts about sexual desires and /or aggressive tendencies provide convenient examples of the kinds of factors sometimes linked to neurotic anxiety.