The child was running, jumping, and laughing.

Meaning: This means that the child was doing all of these actions at the same time. It's like saying, The child was playing and having a lot of fun.

Choice of Words: The is a definite article that refers to a specific child. Was is a verb that describes a state of being or existence. Running, jumping, and laughing are all present participles that describe actions that are happening at the same time. When you put them together, "The child was running, jumping, and laughing" is a sentence that describes the actions of a child who is engaged in multiple activities.