The employer will review your application and may follow-up with you about the job.
The employer will, at a minimum, have your email address. Remember, they are busy and will receive many applicants so doing your best to stand out will increase the odds of being contacted. Simply including a personal message about why you find the company to be a good career fit can mean an enthusiastic response soon after applying.
The employer may also redirect you to a different third-party to complete the application process.