what's the difference between innodb storage engine and innodb plugin

MySQL & MariaDB Other MySQL® Questions
1

Can anybody tell me the difference between the innodb storage engine
and innodb plugin.it puzzle me for a long time!

2

The best resource for learning about this is on [URL]MySQL where there is a clear description of the differences and advantages.

3

How can i know mysql’s default innodb version!For example,if i have a mysql versioned 5.1.37,how can i know it’s default innodb version!