A hypothesis is a possible answer to a question. A supposition.
As you explore your world, you will discover that you have questions you would like answered. These questions may be based on your experiences, previous research, and/or observations.
A hypothesis is a possible answer to one such question. It is a possible answer that you can test and measure in such a way as to determine whether or not it is a true answer to your original question.
For example, perhaps you are wondering why a feather floats in the wind.
You might form and test several hypotheses before discovering the answer to this question.
You will frequently find the concept of hypothesis is over-complicated because people don’t like to prove their hypotheses wrong. Being wrong is extremely educational, but when you are emotionally attached to being right, it can be very uncomfortable.
Additionally, it is much easier to build an experiment to prove or disprove your hypothesis when it is measurable. Your hypothesis should be clear enough that you can design an experiment to prove or disprove it.