Practice is the act of repeatedly doing an action such that a person gains proficiency in doing so. By practicing you gain a skill which is you did not have before.
Conditioning refers to a case of learning where a stimulus which was previously neutral is combined with a stimulant that is biologically potent. For example, feeling nauseous when you smell something bad. This happens due to the fact that previously you smelled something bad which made you sick after eating it. This is almost completely permanent.
