I'm going to try to make this as simple as possible, but it's necessary to give a little information about osmolarity.
Hypo, Iso and Hyper tonic solutions all are compared to the osmolarity, or concentration of particles in liquid, of blood plasma. Think of osmolarity as the amount of grains of salt in a cup of water. Particles can never move, only the fluid can. The fluid wants to balance out the number of particles in the veins and outside the veins. It does this by moving between the veins and the cells.
Isotonic solutions are the easiest. They contain the same amount of particles as blood plasma. So if you had a cup of Isotonic solution and a cup of blood, they would contain the same amount of salt. Because the osmolarity is the same, isotonic solutions stay in the blood stream. So when you give an isotonic solution, it increases the amount of fluid in the veins. This is good for someone who has lost a lot of blood or has low blood pressure due.
Hypotonic solutions have fewer particles than blood. So when you give a hypotonic solution, you have more water and fewer particles in the blood. To balance this, the body shifts fluid out of the veins and into the cells. So hypotonic solutions hydrate cells.
Hypertonic solutions contain a higher concentration of particles than blood plasma. So when you give hypertonic solutions, the body balances out by pulling fluid from the cells and interstitial (between cells) space and into the vascular system. Hypertonic solutions increase the amount of fluid in the veins by pulling fluid from the cells and interstitial space. This might be helpful if a patient has edema.
There are plenty of places online that you can find a list of which solutions are hyper, hypo, iso, so I'm not going to list them. But be careful with solutions that contain glucose (D5 or D10). Glucose is used within minutes of entering the blood stream, so you are left with the base solution. For example, D5 NS is hypertonic in the bag, but the glucose is used to quickly that you are left with the base solution, NS, which is isotonic. D5 0.45NS is hypertonic in the bag, but once the glucose is used you are left with 0.45 NS, which is hypotonic.