Manifestations are really just experiences. Most people understand experiences to be what you observe by using your senses. So, a manifestation is just a real world tangible object, experience, or person that you encounter in your everyday life.
This is important though if you are trying to create the life you have always dreamed of living through the use of the law of attraction. What is manifesting in your life right now, what you are experiencing right now, is simply a manifestation that has resulted from the thoughts you have been thinking and the subjects you have been focusing upon.
When you know this to be true, you can easily understand why certain experiences enter your life. You can also use this truth to measure your progress as you attempt to accomplish a specific goal as well.
For example, lets say you want to own a specific car. So, in order to get the car you want, you start envisioning owning it right now. You imagine touching it, sitting in it, driving it as you do so. By completing this process, you place yourself in harmony with your desire.
Now, you might only do this process for a small period of time each day though. The rest of the day you may give more attention to thoughts of lack and a lot of thoughts that have nothing to do with the car you are wanting to attract. That's life. That's also what you do when you are not an experienced manifestor as well. Once you become more experienced at manifesting your desires, you will understand the importance of keeping your focus on good feeling thoughts and what you truly want in life.
Even if you do not give all of your attention to the subject of owning a brand new car, you are still giving your attention to the subject to some degree if this is a desire of yours. As a result, the Universe has to manifest a corresponding manifestation, or an experience, that matches your point of attraction, the way you feel. You likely already feel pretty good on an average day if you generally give your attention to subjects that make you feel good, but when you are focusing on a car you love, you likely feel really good. So, if you choose to give your attention to really good feeling thoughts about the car you would like to own, the Universe will give you a corresponding manifestation and you may actually see the car you want as you go about your day due to your focus.
Many people might write this small experience off as a coincidence. Some people might even jump into thoughts of lack and feelings of lack in response to this event too, because they want the car so much, but they are focused on what they don't want, the absence of the car in their life.
In reality though, this experience is nothing less than a miracle. You gave your attention to this specific car and it showed itself in your life experience as a manifestation. You should take this as a very good sign, because it means you are doing something right with your thoughts. When you are giving your attention to the car of your dreams and you are feeling good, you are attracting more experiences involving that car into your life.
This holds true for all subjects too. No matter what you want to manifest or experience, you can simply give your attention to what you want through the use of your imagination, and imagine living the life you want to live, and you will receive corresponding manifestations that prove to you that you are moving towards the fulfillment of your desires.