To be pure is to be free from sin. The goal of someone who’s striving to be pure is to please God and to faithfully live according to His word. They put God first above all things and no longer surrender to their sinful nature. Those who are pure aren’t perfect, so they will sin sporadically, however, they never practice sin nor do they tolerate sin in their lives. They recognize sin as sin, they repent, change their ways and continue fighting to remain pure.
An impure person doesn’t care that they are practicing sin. They are not spiritually or eternally minded at all. Contrarily the pure person is fully aware that the decisions we make here on earth determine where we will spend eternity. The ultimate goal of the pure is to spend eternity with God the source of purity. Consequently they do what is necessary by leading a holy and honorable lifestyle here on earth so they will experience eternal life with God in heaven.