Cotton rib fabric is a type of fabric that's characterized by vertical ridges or "ribs". This fabric is often used for clothing items that require elasticity and flexibility, such as tank tops, undergarments, and certain types of sportswear. The ribbing effect is created during the weaving process by alternating high and low tension in the warp and weft threads.

Here are some tips on how to care for cotton rib fabric:

1. Washing: Cotton rib can typically be machine washed in warm water. However, always check the garment's care label for specific instructions, as some cotton rib items may require cold water or hand washing to maintain their shape and color.

2. Detergent: Use a mild detergent suitable for cotton fabrics. Avoid using bleach unless the fabric is white; bleach can damage and discolor colored fabrics.

3. Drying: Cotton rib can generally be tumble dried on a low heat setting. However, to minimize shrinkage and prolong the life of the garment, consider air drying instead.

4. Ironing: If necessary, cotton rib can be ironed on a low to medium heat setting. To prevent damage, iron the garment while it's still damp, and always iron on the reverse side if possible.

5. Storage: Store cotton rib garments in a cool, dry place. Fold them neatly to prevent wrinkling.

6. Stains: Treat stains promptly. Apply a small amount of stain remover to the affected area and gently rub it in before washing the garment. Avoid rubbing too hard, as this can damage the fabric.

Always remember to follow the specific care instructions provided on the garment's label for the best results. Cotton is a natural fiber and may have special care requirements depending on the specific weave and dye used.