A more thorough explanation:

An act can refer to two things in the legal sense:

In criminal law, an act is a voluntary bodily movement that is necessary to prove a defendant's guilt. This is called actus reus. For example, if someone intentionally hits another person, that bodily movement is considered an act. However, if someone accidentally bumps into another person, that is not considered an act because it was not voluntary.

It's important to note that not all crimes require a bodily movement. Sometimes, a failure to act can also be considered an act. For example, if a parent fails to provide their child with necessary medical care, that failure to act can be considered an act of neglect.

An act can also refer to a formal body of law or proposed law. For example, the Clean Water Act and the Civil Rights Act are both acts that contain a collection of provisions related to a specific subject. Proposed legislation can also be referred to as an act.

These examples illustrate how the term "act" can have different meanings depending on the context. In criminal law, an act refers to a voluntary bodily movement, while in legislation, an act refers to a formal body of law or proposed law.