You are right about the first part. Sha-256 is a hash function, but it's not symmetric encryption.

<p dir="auto">symmetric encryption dictates a given key <code>K can be used to both transform plain text into cipher text and vice-versa. <p dir="auto">A hashing function cannot be reversed because it's a large to small key space function, meaning it's only one way, there's no reversing a hash, unless you try all possibilities until you get the result. <p dir="auto">There are publica tables on some hashing algos, they are giant covering hashs for the most known combinations. <p dir="auto">But, a SHA-256 as the name suggests generates a 256-bit output. <p dir="auto">Since one bit can be represented with two distincts values (i.e. 0 and 1) <p dir="auto">we have all the possible combinations being <code>2^256 which is a number I not even know the name. <p dir="auto">about the string password, that a myth that must fall at any cost. <p dir="auto">Humans can NEVER produce strong passwords. It's up to the software engineers and cryptographers to move from a low entropy input to a large entropy input while balancing the computational recurrent cost. <p dir="auto">:)