Agoraphobia: fear of crowds or fear of open spaces?

Fear of both: Agoraphobia was initially characterized as a fear of open spaces. Currently, it is an anxiety disorder where a sufferer is afraid of difficult, or embarrassing situations from which he cannot escape, or obtain enough assistance or reassurance to feel secure. It is often related to panic disorder where the sufferer may be so fearful of panic attacks to the point of becoming unable to leave home.

Neither per se: A common misperception about agoraphobia is that it is a fear of open spaces or crowds. Agoraphobia is actually a fear of places or situations where escape is perceived to be difficult in the event of having a panic attack. In other words, places are avoided due to "what if i get there and have a panic attack?! no one can help me!".

Agoraphobia: Both crowds or open spaces can be major parts of agoraphobia.