String tension

learner

At the risk of seeming an nincompoop, I am puzzled by the string tension comments on various threads. I am under the impression that an A=440 is just that. A string length of any material that vibrates at 440 cycles will create an A pitch. I am confused about the 'high tension' comments regarding Evah Pirazzis and other strings. While I can discern differences between string brands, I attribute them to the material being used and the feel they have under my fingers. A gut core and a synthetic core have different feels, while the metal used for the winding is also a factor in the strings I use.

I would appreciate an explanation what 'high tension' versus 'low tension' means.