jar java spring spring-boot war

Differences between jar and war in Spring Boot?

I’m about to build my first website in Java with Spring Framework using Spring Boot and it’s much easier to build it in jar, but I have a few questions about it.

What are the differences in general?

In jar files the views are under /resources/templates, but in war file it’s under /webapp/WEB-INF/.

What are the differences? Can I deploy a jar on an online host?