There are a number of ways to categorise bonuses. There can be overlap between categories.

what does the bonus affect?

• economic

• military

Is a free blacksmith tech a military bonus or an economic bonus? both? I would say military. Regardless of problems (grey areas; taking to extremes), this is a useful dichotomy.

when does the bonus occur?

• early game

persians starting with +50 wood and food

• late game

vietnamese imperial skirmisher upgrade

• whole game

celts collect wood faster

how long does the bonus last?

• head start (i.e. once off; the opponent will "catch up" after getting the tech)

burmese free lumber upgrades; magyar free blacksmith techs

• permanent boost (i.e. continuous)

celts lumber bonus; burmese infantry attack bonus

The easy way to see the difference between a "once off" bonus and a "continuous" bonus is to ask "could this realistically have a noticeable effect in a full pop, post-imp scenario?"

Regarding continuous bonuses, is the bonus dynamic or static?

• dynamic continuous

huns cheaper cav archers; britons archer range bonus

• static (or limited use) continuous [these bonuses are rare]

huns pop bonus; goth pop cap bonus; nomads; arguably atheism (wonder/relic part)

both dynamic continuous and static continuous bonuses have an effect in a full pop, post-imp scenario. To differentiate between the two ask "can I (currently and in the future) increase or decrease my usage of the bonus?" If "No" then the bonus is static.