3 elements, carbon, hydrogen and oxygen, are non-minerals. Carbon and oxygen enter plants through leaves as carbon dioxide. Oxygen also enters plants with hydrogen through roots as water.
14 are minerals. The 14 must be dissolved in soil water and enter the plant as roots take up water. Mineral elements can further be divided into primary or secondary macronutrients and micronutrients.
Macronutrients are those needed in relatively large amounts while micronutrients, as their name implies, are needed in small amounts. However, a deficiency in any vital element can seriously inhibit plant development.
Once inside plants, nutrients are transported to where they are needed. Once incorporated by the plant, some elements can be immobile while others can be remobilized.
Immobile elements essentially get locked in place. Those that can be remobilized can leave their original location and move to areas of greater demand.