Conversations with newbs (continued from the Bughouse)

[Steel Mirage]

I get that. Thats really useful, thank you. But I'm just wondering how the tech level interacts with prerequisites, or if the tech level is the mechanism for prerequisite setting. For example, can your infantry tech level be at a different level than your unit tech level, defense structure tech level, aircraft tech level, naval tech level, etc?
I swear I'm not trying to be obtuse or n00b-like, just shooting for comprehension.

EDIT: Just downloaded Launch Base, reading through the Ares 0.2 Manual, an exceedingly helpful publication. Imagine that...