Veracrypt enables the user to create and maintain an on-the-fly-encrypted volume (data storage device). The term "On-the-fly" refers to the ability of VeraCrypt to automatically encrypt data before it is saved or decrypt data just before it is loaded into memory without user intervention. Data stored on an encrypted volume can only be read if the correct password or encryption key is used. VeraCrypt is based on the now discontinued Truecrypt and can load TrueCrypt volumes
Be sure to read the VeraCrypt Online Documentation before installing.