Distinguish offer from General offer and An invitation to offer?

An invitation to treat is an action inviting other parties to make an offer to form a contract. These actions may sometimes appear to be offers themselves, and the difference can sometimes be difficult to determine. The distinction is important because accepting an offer creates a binding contract while "accepting" an invitation to treat is actually making an offer.

Advertisements are usually invitations to treat, which allows sellers to refuse to sell products at prices mistakenly marked. Advertisements can also be considered offers in some specific cases. Auctions are sometimes invitations to treat which allows the seller to accept bids and choose which to accept. However, if the seller states that there is no reserve price or the reserve price has been met, the auction will be considered an offer accepted by the highest bidder.