Table salt is comprised of almost purely sodium chloride molecules that are typically mined from mineral deposits. Table salt often contains added iodine, which is necessary for normal thyroid functioning.
In contrast, sea salt can range from fine-grained to large crystals and is produced by evaporating seawater. It can be found in most grocery stores, but is significantly more expensive than table salt. While it is different from table salt in that it has trace amounts of other minerals resulting in its varied flavors, it is still sodium chloride. The sodium content is comparable between table salt and sea salt, and the small amount of minerals has no known healthful effects. One teaspoon of table salt contains 2,400 mg of sodium, while one teaspoon of sea salt contains 2,250 mg of sodium.
Sea salt is sometimes preferred during cooking because it adds a slightly different texture and taste, but from a nutrition perspective, there is little or no benefit from choosing sea salt.