Like I mentioned earlier, a good example is a students-courses relationship. Our business use case is Affiliates and Deals—that works alright, too.
Just remember, in most cases there are better workarounds than using a multi-select lookup field. In fact, I build one in this video.
Instead of using multi-select lookup, I simply create a custom module called “Referrals” that has lookups to both the Contacts (the Affiliate) and the Deals modules. This serves as a bridge between the two and is often easier for people to understand than the multi-select lookup field itself.
