An Encryption Trojan is a so-called Ransomware Trojan that encrypts the entire PC or individual data. They are also colloquially called cryptotrojans or ransom trojans. The ransom Trojan then asks you to pay a ransom in order to decrypt the data again.
Often you will also be asked to pay the ransom within a short time window, otherwise the ransom will double or the data will remain encrypted forever. In all cases – keep calm and call in experts as quickly as possible!