Talking about SEO and SEM

But how exactly should we talk about SEO and SEM ?

if you consider certain points of view, SEO is part of the SEM strategy, so we can include SEO in SEM. Yet, others consider that even the link building part is called "optimization"

What do you think ?

My opinion is that SEO is part of SEM as the link building part can be considered a promotion -> included in SEM.

Optimization can be done from certain points of view :
- titles
- internal linking structure
- content
- keywords frequency
- etc..