They come in all shapes, colors and sizes. Some are permanent marker while others are erasable. Highlighters are also marker pens and are used to highlight and cover over existing words. Non permanent markers are normally used for whiteboards in schools or conferences and meetings.
Now, I thought with the prevalence of marker pens (I remembered the use of it even back then when I was in U of T in Canada, that was long ago!), white chalks are gone and obsolete. To my surprise (and horror), I actually found professors in Peking University using those!!! Oh boy, isn't those thing "poisonous" and detrimental to health?
I haven't seen security and election markers so I don't have any idea how effective those are. In any case, I use marker pens mostly when I pack my stuff for moving! How about you?