Otherwise just the information will be enough. One way of using a comma is to join two dependant, or subordinate clauses. That means a group of words that can not stand on their own. For example, phrases that do not have nouns or verbs in them are dependent on other phrases that do. On the other hand, in the mean time, for example, in other words, are all phrases that depend on other phrases.
Commas are important in order to separate words or objects in a series.
Here is an example. The grocery bag contains eggs, milk, bread, cheese, and crackers. A writer can decide whether or not the comma after cheese is necessary, but it is important to understand that without the comma the last two items may be viewed as a single item. The grocery bag contains eggs, mild, bread, cheese and crackers . The cheese and crackers might actually come in the same package.