Can you explain how to proliferate loyalty counters on planeswalkers in Magic: The Gathering?

To proliferate loyalty counters on planeswalkers in Magic: The Gathering, you can use cards or abilities that have the "proliferate" keyWord. When you proliferate, you can add an additional loyalty counter to each planeswalker you control that already has one. This can help you increase the loyalty of your planeswalkers and make them more powerful.