Your credit score reflects your creditworthiness, or how likely you are to pay back your debts on time. The higher your score, the better your estimated creditworthiness.
Your credit score might be checked when you apply for:
A new credit card or loan
Auto or home insurance
A new job
A new cell phone or utilities account
Credit scores are calculated by credit bureaus (like TransUnion and Equifax) according to specific scoring models (like VantageScore 3.0). Because each bureau has its own credit file on you (known as your credit report) and each scoring model weighs your credit details differently, your scores can vary from bureau to bureau and model to model.
Credit Karma provides two credit scores. Both use the VantageScore 3.0 scoring model. One is calculated by TransUnion, the other by Equifax.