I see on many technologies an increase of +1 or +2 (of various stats) on tundra, arid, and planet. I understand what tundra terran etc. are. What the world (he he) does planet mean? If it is any planet why list tundra, desert, etc? Very confused.

+X of Y on planet means that the bonus applies for any type of planet. Some improvements (e.g. all planetary exploitations) may also list additional bonuses for specific types of planets. In general, Amplitude chooses to express these bonuses in the smallest possible number of single-condition items. For example, the level-3 food exploitation provides +3 food per population on all planet types, but it provides a total +6 food per population to terran, jungle, or ocean planets, since they receive a further +3 bonus.

Thank you so much...

Its in there to make exploits other then the optimal ones a possebility in case you desperately "need" other exploits. Otherwise they wouldnt have bothered to put a choice in there in the first place.

When you mouse over the option it says about needing the xeno tech before you can trade technologies. I thought this was toggling that requirement. I have to admit the pop ups in this game are often more confusing than if they weren't there at all.