What will happen if I will copy the information from encrypted hard drive? Will it be store decrypted?

It will be stored as plain files; FileVault encryption only protects files when thy're on your startup volume. You can encrypt the external drive if you want. You can also create an encrypted disk image, store the image on the external disk, and then store files inside the encrypted image. But unless you do something to encrypt the files, they'll be freely readable from the external disk.

BTW, the same is true of Apple's Time Machine backup system -- backing up a FileVault-protected Mac results in an unencrypted backup unless you choose the option to encrypt the backup.

FileVault doesn't encrypt single files but whole volumes. So after unlocking the volume the files itselves appear as not encrypted. Copying the files (as part of a backup) will save them unencrypted on a normal backup volume. Copying them to an encrypted but unlocked backup volume will save them also as "not encrypted". After locking the encrypted backup volume they are safe again though.

Files are not encrypted with FileVault, the disk is encrypted and it's not always easy to understand the difference.

But what it means, in practice, is if you copy a file from a FileVault-protected drive on your Mac to an external drive:

1) which is not FileVault-protected, - the file will be accessible on your Mac - the file will be accessible on any other machine (Mac/PC) which you might connect the external drive to.

2) which is FileVault-protected - the file will be accessible on your Mac - the file will NOT be accessible by another party who, with/without your permission moves/steals the drive - the file MAY be accessible by you on another Mac, but you will need a password (I'm just not sure which one)