All of the things listed in this box have the force of law (i.e. you can get in legal trouble for violating them) and are sometimes what is meant when someone refers to "the law."
Act, Law, and Statute mean essentially the same thing. They are created by the legislative branch (Congress or the state legislature).
A Bill is a proposed law. Popular names can be confusing here. For example, the Paycheck Fairness Act was the name of a bill that never became law, and the Brady Bill became a law but is still known by its famous popular name.
Rules mean the same thing as Regulations and come from the executive branch (e.g. EPA, Labor Department, Washington Licensing Department, etc.)
Executive Orders and Proclamations are produced by the President or the Governor. In modern times proclamations are usually feel-good announcements with no force of law (e.g. proclaiming Thanksgiving), but this was not always true. For example, some Indian reservations were created by presidential proclamation.
Decisions and Rulings come from the judicial branch (i.e. courts) and are often expressed by written opinions.
See also the Law Resources page.