What are the characteristics of a red giant star?

Cooler, Giant, forms ring called planetary nebula

From nuclear fusion ##rarr## The energy released by heating of the helium core causes the outer hydrogen shell to expand greatly. As the outer shell expands, it cools and its color reddens. The red color indicates that it is cooler than the other star. It is a giant because the star's outer shell has expanded greatly from its original size. ##rarr## As the helium core starting to fuse into carbon atoms,the last hydrogen gas surrounding the red giant drift away. This drifting forms a ring around the central core of the star. the ring is called planetary nebula. This is the planetary nebula.https://www.google.com.ph/search?q=red+giant+star&biw=1093&bih=514&source=lnms&tbm=isch&sa=X&ved=0CAYQ_AUoAWoVChMIz_CQhbGbyQIVhp6UCh23TA8htbm=isch&q=red+giant+star+planetary+nebula&imgrc=64pSMb3J5ErhOM%3A

This is the red giant star compared to our sun.https://www.google.com.ph/search?q=red+giant+star&biw=1093&bih=514&source=lnms&tbm=isch&sa=X&ved=0CAYQ_AUoAWoVChMIz_CQhbGbyQIVhp6UCh23TA8himgrc=t384eTlhQ7D01M%3A