You use us every day. Most times you use us, it's in a different way and at a different time. Sometimes you use us individually, but for the most part you use us together, for we work much better that way.
Although we are all different and have different names or spellings, we are still as we are. We even have different variations of ourselves for others to use, but not everyone can actually use other variations without actually knowing what they are to begin with, or how to use them.
By now you have either a total look of confusion on your face, or a smile of knowing. Either way, the answer stares you directly in your face!
So...
**tilts head**
...What are they?