What are the possible star fuels? I always thought the only fuel for a star was hydrogen, which is fused into helium.

But while reading some questions and answers here in ASO, I saw phrases like "This balance stays relatively stable until the star runs out of whatever its current fuel is".

Besides hydrogen, what are the possible fuels in a star’s core?
As a star begins to age and exhaust its hydrogen supply, pressure will build in its interior until temperatures rise enough to begin fusing helium into carbon. If the star is massive enough, this process will continue, using heavier elements each time.

Referring to this link on stellar fusion, depending on their mass, stars use a variety of elements from hydrogen to silicon as 'fuel'. Stellar cores of stars towards the end of their giant stages will have cores of iron, but iron doesn't fuse into anything heavier in a stellar core.