Table salt is made of sodium and chloride.
While sodium is important for muscle contractions and water balance, too much can cause problems for some people. People who are salt sensitive may see their blood pressure go up when they eat too much salt. Some people retain fluid with too much salt. Unfortunately, at this time there is no way to determine if you're salt sensitive until you notice its effect. The best plan is to learn where to look for salt and try to moderate the amount you eat.