Protecting a page means to prevent normal users from editing (and/or moving, and/or reading) it. This should only be used as a last resort method to end editing wars, to protect continuously vandalized pages, or to make sure only higher ranking users can edit a page (for administrative reasons).
Make sure the reason you give for the protection is complete and reasonable, so other administrative personnel understands what you were doing when they see the protection on ModEnc:Protection log.
Pages should be unprotected after the disputing sides have come to an agreement, or after a reasonable amount of time to assume disputing parties or spammers have lost interest in them.
If you are part of one of the disputing parties, please ask another Riot Control Officer to decide over protection or unprotection, so your independent point of view in administrative matters is not compromised. Under no circumstances use your administrative powers to win an argument or edit war.
Protection is an extreme measure. Make sure you think about your decisions.
Big SysOp is watching you.