You can use labels for anything you desire but usually they are used for tracking what messages you have sent to which fundraiser.
You can use labels for anything you desire but usually they are used for tracking what messages (or stewardship strategy) you have sent to which fundraiser and for anything specific about that fundraiser you want to "tag" for later (ie an influencer or someone of importance)
You can find and add new Labels by going to Account Settings > Labels/
Labels can be added individual fundraiser records (and donate button post records). You can add multiple labels to each fundraiser (or donate button post).
In both the Fundraiser Export to CSV file and also in the Fundraiser Type report in Report Builder, labels for a fundraiser will all appear in the same column, separated by a comma.