Posting
In one sentenceTransferring the amounts of entries from the general journal to their accounts in the general ledger, each amount to its debit or credit side, so that each account's balance appears.
Simply put
The journal tells the story of transactions in the order they happened, but it doesn't tell you how much is in the cash box now. Posting collects each account's movements in one place, so you know its balance at any time.
In accounting software, posting happens automatically when the entry is saved or approved, so your role is to review the entry before it is posted, because changing it afterward requires a correcting entry.
Example
A store sold goods for cash for 5,000 SAR, and the entry was recorded in the journal: Dr Cash, Cr Sales. On posting, 5,000 is written on the debit side of the cash account, and 5,000 on the credit side of the sales account.
Don't confuse it with
Journal entryThe entry is the first recording of the transaction, and posting is a later step that transfers it to the accounts.