What is the difference between participants, donors & pledgers?

GiftTool uses the following terms in regards to the Pledge-a-thon service:

A participant registers to participate in your Pledge-a-thon event and/or become a fundraiser. They can set up their personal fundraising pages, and actively participate in raising funds for your organization. Although a participant automatically receives their own fundraising page, they are not obligated to fundraise. Furthermore, they can make a donation to support their own fundraising efforts.
A donor or pledger support the organization by donating through participants. They may not be involved with the pledge-a-thon other than to make a donation.