Despite being technically undead, you still require things like food, water, and rest; though the rules are maybe a little different than what you're used to. This is largely because the spellwork which binds your physical form together still thinks you are alive.

Sleep
You still require sleep, though only one short rest every 24 hours to stave off Exhaustion. See Racial: Rest and Reconstitution for details.

Food and Drink
The spellwork binding your form together requires maintenance to continue, and therefore you must draw sustainable from food and water. However, you need only the ability to convince yourself that what you are eating will both be enough to sustain you, and that you can consume it without issue. Therefore, if you think you can eat meat that is clearly rotten, you can do so without danger. If you think you can eat less edible things, (as long as you can justify it to your Game Master through roleplay) such as stone, wood, or steel, you can also do that. Likewise if you don't think you'll get drunk from drinking an entire swimming pool of ale, you may do so as long as it will fit, without danger.
Materials consumed in this way appear to float within your ribcage (if your ribcage is visible) and slowly dissolve, as they are consumed.

As a creature whose existence is supported using a skeleton infused with runes and magic, you are technically undead... but also not. 

You were not created using necromancy, though a soul was used to solidify the magic which formed you, you do not rely on necromantic energy to continue your existence. 

Therefore, despite your appearance you are basically, meaningfully indistinguishable on a functional level, from whatever race your bones were harvested from. 

That being said, you don't possess any of their racials, such as a flight speed, or dragon's breath, but you might possess some of their physical characteristics, such as red bones, horns, or a taller figure.

Your relative size is medium, however depending on what skeleton you were made from, you might function a little differently. What kind of skeleton are you? 

When you regain hit-points from rest, you may add 1d6 to your pool of hit die. This ability is refreshed at dawn as long as you have had a long rest the previous day, or were in the midst of one when dawn came.
Also, while you still require sleep, but you only need a short rest, once every 24 hours to stave off exhaustion.