Andrew Dorokhov
Right after broadcast, a payment often shows as unconfirmed: it has propagated on the network but is not yet in the blockchain. A miner must include it in a block. New blocks appear roughly every 10 minutes; once included, the transaction is confirmed and can be spent further. Visibility is immediate; trust grows when the transaction is in a block (and after more blocks pile on top — additional confirmations).
Common misconception
People often assume you must wait ~10 minutes for one confirmation, or ~60 minutes for six. Confirmations do increase network-wide finality, but that delay is not required for every small payment (e.g. a coffee). A merchant may accept a valid low-value transaction with zero confirmations, with risk comparable to a card payment without ID or signature.
Stuck transactions
Services such as open_in_new ViaBTC can help accelerate (push) a stuck transaction.