Also, were these techniques often used for interrogation with the purpose of retrieving information, or was the act more of a punishment, with information being a possible benefit?

The answer would be extremely dependent on the time and place... Unfortunately for this thread, "medieval" is an extremely large time and place. It really depends on who is in power; some rulers were sadistic while others were rational/kind.

I recently had to look into the punishments for heresy in France before the Revolution and discovered that judicial statistics were a fairly recent invention, at least in France. There, it started a bit during the revolution but the first good stats date from the First Empire.

So if you are asking for statistics regarding petty crimes and common people, I think that your question will be very hard to answer. Most of the sources we have will focus on prominent figures or political trials, not the average person.

Well it's obviously impossible to generalise about the medieval period in general, but if you take medieval/ early modern England, there were certainly physical punishments such as the stocks or trials by ordeals that ordinary people could suffer. 'Actual torture' though, was thought of mainly as the rack or manacles, which became popular in the Henrican period and as far as I know was pretty much only used to uncover supposed political or religious sedition.

This wasn't universally true though, there were a few cases where hanging by manacles was used to question thieves and Gypsies in the Elizabethan period, so authorities definitely could torture people for a variety of reasons, but rarely did.