Thoughts are your original content.
Thoughts are written by you in contrast with other content which is perhaps captured from external sources. Thoughts are simple blog posts using the Standard Post Format.
They are important in the sense that they are already assembling bits of knowledge. When you write about something you express your opinion about the subject thus create knowledge.
In Log Lolla Pro Thoughts are the most natural way to create knowledge. Next to them are Summaries which require other type of thinking.