RememBear encrypts your items using both your Master Password and a unique device key generated by the application. It stores your items, including passwords, in an encrypted file on your device and on their secure servers for sync and backup purposes.
That said, RememBear will only encrypt and decrypt the items on your physical device. This means that your passwords and other items are always encrypted during syncing and remain encrypted when in the storage on their secure servers. You and only you are ever able to access your items as long as you keep your master password private.