The form that a human can read is called source code. It is what a human programmer creates, and is translated by another computer program into the binary or executable form. The right to study means that the software itself must be made available in a manner that humans can read, as source code. The right to modify is the right to fix a problem or enhance a program. For most people, this means your right, or your organization's right, to hire someone to do the job for you, in much the same way you hire an auto mechanic to fix your car or a carpenter to extend your home.
Modification is helpful.
Application developers cannot think of all the ways others will use their software. Developers cannot foresee the new burdens that will be put on their code. They cannot anticipate all the local conditions, whether someone in Thailand will use a program first written in Finland. The right to redistribute means that you, who own a computer, a software factory, have the right to make copies of a program and redistribute it. You can charge for these copies, or give them away.