Difference between isotonic, hypertonic and hypotonic solutions

Transport across the Cell Membrane  What is the major difference between passive and active transport? What does a "selectively permeable membrane" mean? What are the three types of passive transport? Describe each. Why can’t all molecules go through a cell membrane? Which types of substances can? Explain the difference between isotonic, hypertonic and hypotonic solutions. Use red blood cells to explain your answer. (Hint: you can also draw a diagram to help explain your answer)  What does a concentration gradient mean?  What is the difference between endocytosis and exocytosis? Review the processes for the different types of passive and active transport!