SQL Server: What is the difference between Index Rebuilding and Index Reorganizing?

Question

What is the difference between Index Rebuilding and Index Reorganizing?

Answer 1

"Reorganize index" is a process of cleaning, organizing, and defragmenting of "leaf level" of the B-tree (really, data pages).

Rebuilding of the index is changing the whole B-tree, recreating the index.

It’s recommended that index should be reorganized when index fragmentation is from 10% to 40%; if index fragmentation is great than 40%, it’s better to rebuild it.

Rebuilding of an index takes more resources, produce locks and slowing performance (if you choose to keep table online). So, you need to find right time for that process.