Someone has chargebaked a payment. Paypal will review this transaction and if everythings is ok they will make that money available to you.
Most of the time, it means Paypal f*cked you in the *ss. Technically, it means a person (buyer) sent you a payment, then issued a chargeback (saying they aren't happy with the item(or more commonly, an unauthorized transaction, as they are trying to scam you))
Yeah, i've already closed the dispute. PayPal was asking me where i've shipped the product, etc... The buyer told me that this is because his account must be verified (proof of address) then the dispute will be closed...