One major difference is that pre-qualification only requires a soft inquiry on your credit. This means that your credit score won’t be impacted when the lender pulls your credit score. In contrast, getting loan pre-approval requires a hard inquiry, which can impact your credit.
To get a pre-qualification, you’ll need to fill out an online application to the lender. You’ll need to estimate your income and financial status— and while it may be tempting to fudge these, you won’t get an accurate idea of what type of loan you’re actually qualified for unless you give exact numbers.