Theme-writing best practices: Blocks, Segments, Templates, and their differences.

[laundmo]

Heyo,

i've been trying to make my own theme by modifying and combining parts of other themes. From looking at a few, and reading the docs, I wasn't able to figure out a few things regarding when to use which concept.

1. Why do some themes like pure have multiple blocks with the same block-level options (same alingment, same type) only differing in segments?
   1. Whats the effect of doing this?
   2. When does it make sense to have separate blocks with the same config? How do i decide which segments go into their own block?
2. Conceptually, what is the difference between a Block and a Segment? I understand that some options are block-level and some segment-level, of course, but how should i think about them? (perhaps i'm only confused because the pure theme does something nonsensical?)
3. Lets say i want to do user@host with different colors for each of user, @ and host. How do i decide between a single segment with a template which sets the colors for each part using the inline color syntax, vs 3 segments, one for each of the things i want to color differently?

I hope i haven't just missed a part of the documentation that explains this

Thanks for this project, i've been using it for years (tho with pre-made themes).