Even the greenest beginner in genealogy is familiar with vital records. It's a general term used for birth, marriage and death records. These documents are the foundation for any genealogy studies.
These records can provide a lot more information than just a name and date. If you have access to the original certificates or registrations, you will find a wealth of information. Of course, the specifics will be different from region to region, since record-keeping practices of this kind are not standardized.
A birth registration can give you a lot more than just a person's name and date of birth. You'll also find parents names and possibly their occupations. You will also find out the specific place of birth, and even the attending physician. If you are looking into the health-related history of your family, then finding the name of the family doctor can be helpful.
Marriage records are even better. Not only will you get the full names of bride and groom with the date and place of the marriage, but also their ages (or birth dates) and further information on their parents. Place of birth and occupations are also often included. You might also learn that either bride or groom have been married before, leading you to discover a previously unknown spouse.
Death records are usually a little sparser. Full name and age, with date and place of death are the basic details. Cause of death can be interesting, especially if you are curious about any inherited health conditions. I seem to have a lot of ancestors who die of pneumonia and syncope of the heart.
So even if you know a person's birth or death date, you might find new information from original vital record documents. And as I mentioned in my article on watching for errors, don't always trust a transcribed version of any document. Vital records are usually hand-written, especially the older ones, and there can be frequent errors when they are added to online databases. Being able to see the original (or at least a scanned image of the original) is always the best bet.