1. "One who is practicing neither for his own welfare nor the welfare of others." This person could be labeled the beginner, who is curious about meditation. They try it out to see "if it's a good fit."
2. "One who is practicing for the welfare of others but not his own welfare." This is the over idealistic individual who is dedicating his meditation entirely to others. "I'm doing this for you!" type of attitude.
3. "One who is practicing for his own welfare but not the welfare of others." Here are the people who come to meditation solely for their own benefit: those coming because they have too much stress in their lives, they're suffering from anxiety and need relief, or they suddenly find themselves with a life threatening diagnosis so they want to heal mind and body via mediation.
4. "One who is practicing both for his own welfare and fore the welfare of others." Here, the Buddha pauses in his teaching, to add this wisdom: "The person practicing for both his own welfare and for the welfare of others is the foremost, the best, the preeminent, the supreme, and the finest of these four persons."