Lets cut to the chase and break down 7 different types of protein to help you better understand when and why you should take them.
1. Whey Concentrate
When most people refer to protein powder this is what they are talking about. Whey concentrate is one of the most basic types available, and with that it is the most cost effective. It can be used pre and post workout, and throughout the day as a meal replacement. It is not recommended for use before bed.
If you're a beginner or just looking to pad your wallet, whey concentrate is a great option.
2. Whey Isolate
One of the quickest absorbed proteins you can buy, but not the quickest! It is more readily absorbed than its whey concentrate counterpart. A more expensive alternative, but not the most expensive. Whey isolates are usually very low in carbs/sugars which is very useful if you are on a lower carb diet.
Can be taken pre and post workout to give your muscles the nutrients they need to grow and recover.
3. Hydrolysate Protein
The Patron of proteins, hydrolysate is the highest quality available and the most expensive. It provides peptides that are highly absorbable and it has a powerful anabolic (muscle building) effect. Hydrolysate protein is also much easier on the digestive system for those that have troubles digesting protein (aka bad protein farts!). Can be used both pre and post workout.
4. Casein Protein
This is the slowest digested protein that will "trickle feed" your muscles for hours on end. It is a great supplement to take before bed to help with muscle recovery and growth. Casein protein takes 5-7 hours to fully digest so having a shake right before bed will help keep your muscles fed throughout the night. Casein can also be taken throughout the day to help keep you full. It is not recommended for immediately post workout.
5. Milk Protein Isolate
Contains both whey and casein proteins, and is high in amino acids (similar to soy protein). It is usually found in a blend with other proteins and is not preferred choice when looking for a protein. It can be taken throughout the day, but is not recommended at night.
6. Soy Protein
A great source of protein for vegetarians and is loaded with other beneficial ingredients such as glutamine (to help recovery), BCAA's (branched chain amino acids - also help with recovery), and arginine (helps dilate blood vessels, which allows nutrients to get to muscles faster and more efficiently).
7. Egg Albumin
Back when protein powders were non-existent, egg whites were a popular source of protein that are loaded with egg albumin. It contains a great amino acid profile that helps build lean muscle mass. Egg albumin is not generally bought in powdered form, but rather in a carton (egg whites) and cooked. It is also found in many protein blends and mass gainers, and can be taken throughout the day but is not recommended for before bed.
There are many types of protein and it can be very overwhelming for beginners. The best bet for someone just starting out is a whey concentrate as it is affordable and very basic. As you get more serious about bodybuilding you may move towards a hydrolysate, but it will cost much more.
For individuals that are lactose intolerant, a great suggestion to try would be whey isolate. It is still pretty cost effective, and doesn't leave out those who have a problem with lactose.
Whatever protein you chose, make sure you give it time before evaluating its effectiveness. Give it a solid month or a full tub before you evaluate your strength gains for instance. It is not a supplement that you "feel" working, like a pre workout for example. Evaluate your results after a month and go from there.