开户 is a separable verb (离合词) meaning 'to open an account' (bank, brokerage, etc.). The verb 开 and the noun 户 can split when you insert a measure word, duration, or other element between them — for example, 开了一个户 ('opened an account'). You can also say 在银行开户 ('open an account at a bank') without splitting. The object (which bank, what type of account) typically goes before the verb or after the whole phrase.