They influence your maximum health, magicka regeneration rate, running speed, and more.
HP, the red bar, is your maximum health.
It depletes whenever you take damage, resulting in death if it’s reduced to zero.

Magicka, the blue bar, is consumed whenever you cast a spell.
The amount of magicka consumed varies per spell, with stronger spells usually requiring more magicka.
Fatigue, the green bar, determines how much physical action you could take before you become exhausted.

This is also referred to as stamina.
And that’s a wrap on the basics behind Attributes in The Elder Scrolls IV: Remastered.