When you apply for a credit card or loan, creditors need a quick way to determine if you're trustworthy.

How do they do it?

Before the invention of credit scores, they had to get creative. Creditors relied on anything from letters of recommendation to financial background checks, and some just used their personal judgment.

Thanks to FICO, things have changed. FICO gave creditors a way to quickly assess your borrowing eligibility with a three-digit credit score that reflects your history of paying back debt.

Today, most creditors still use FICO Scores, but around 10% now use VantageScore credit scores instead. And the score they choose can affect your chances of being approved.

Fair Issac and Company (FICO) is the company that developed the first credit score model back in 1989. When it comes to credit scores, FICO is the gold standard — their scores are used in an estimated 90% of lending decisions today.

As far as how your credit scores are calculated, FICO considers several different categories of information in your credit reports and weighs each one differently. For example, your payment history makes up 35% of your FICO Score calculation, while your length of credit history only accounts for 15%.

While some versions of the FICO Score range from 250 to 900 points, most range from 300 to 850. For the most widely used version of the FICO Score — the FICO Score 8 — the maximum number of points you can obtain is 850.

Regardless of which version of the FICO Score you pull, you don't need to earn a perfect 850 score to have good credit. According to FICO, anything between 670 and 739 is a "good" credit score, while 740 to 799 is "very good."

If FICO is the veteran of the credit score world, VantageScore is the up-and-coming rookie.

VantageScore is a credit scoring company created by the three major credit bureaus (Equifax, Experian, and TransUnion) in 2006. Its goal is to produce scores that are the same for consumers across all three bureaus.

Similar to FICO, VantageScore credit scores are pulled by creditors to help them determine if you qualify for credit cards and loans. They're also based on the information found in your credit reports, including your payment history, debt balances, and applications for new credit.

VantageScore and FICO consider the same factors when calculating your credit scores, but they weigh them somewhat differently in each of their scoring models. As a result, there can be variation between your FICO and VantageScore credit scores, or even two scores from the same company.

Here are some of the other main differences between the two:

• Popularity/market share: FICO is better established in the credit-scoring industry, and far more creditors rely on FICO to make their loan and credit card decisions.

• Generating new scores: If you have limited credit history, you may have VantageScore credit scores but not FICO Scores. That's because VantageScore can generate scores as soon as you open your first debt account. With FICO, it takes six months.

• Points awarded: In the past, it was normal to have VantageScore credit scores that were higher than your FICO Scores, but now it can go either way. The average FICO Score is currently 715, and the average VantageScore credit score is 702.

There's a good chance you already have free access to at least one version of your FICO or VantageScore credit scores, since many banks, credit unions, and credit card issuers provide it as a perk for their customers.

If not, you can sign up for Chase Credit Journey for a free VantageScore or CapitalOne CreditWise for a free FICO Score — even if you're not a Chase or CapitalOne customer.

Additionally, you can see your free TransUnion VantageScore by signing up for My Money from Yahoo Finance.

If you need more options, try one or both of these:

• Check the VantageScore website to see if your financial institution provides free VantageScore access.

• Sign up for FICO's Free Plan to get access to your FICO 8 Score.

VantageScore credit scores are different from FICO Scores, but they're not more accurate. In terms of popularity with creditors, FICO Scores are used by creditors far more often.

The majority of lenders use FICO credit scores when determining if you qualify for loans, including mortgages, car loans, and personal loans.

There's no way to convert a VantageScore to a FICO Score, or vice versa, since each company has its own way of calculating credit scores.