Difference between reshape and compaction

What is the difference between reshape and compaction in scylla? Even after checking the related documentation, I don’t quite understand.

Is it correct for reshape to do the following?
reshape: To make compaction work well per shard, reshape sstables to fit critica before bootstrap. In the case of stcs, set sstable count for 4 to hit min_threshold , and when using LCS adjusts the sstable size to 160mb.
If the node is restarted after draining it, the reshape operation occurs before node join, and compaction seems to operate after node join. Why does this work like that?

Reshape is a Rewrite of a set of SSTables to satisfy a compaction strategy’s criteria. For example, restoring data from an old backup or before the strategy update.
Reshape happens when the data is wildly out-of-shape and regular compaction would require a lot of work to get it back into shape. It is an offline operation which allows the system to devote all resources to the work.
Regular compaction happens when the data gets somewhat out of shape (e.g. a new sstable is added when a memtable is flushed). It’s an online operation that requires mild resource use.