Tech points are used to purchase Technology upgrades, and can only be lost if you reset your game.
How do I earn Tech Points?
Tech Points can be earned by having Scientists research at the Research Table. The more experienced your Scientist is, the more tech points they will earn. They can also be found in certain events around the Island, watching ads, and in Random Events. You can earn them faster by upgrading the Research Technology and also by purchasing one or more of the Science Totem. You can also purchase Tech Points using Lavastones.
What do Technology Upgrades do? Do I need them?
Technology Upgrades allow you to progress in the game by unlocking more advanced levels of each of the technologies. For example, the rate you can earn Tech Points is boosted by upgrading Research and with each Medicine upgrade your villagers will live longer, healthier lives.
What are Totems? Do I have to buy them?
Totems are, essentially, permanent power-ups that you buy with Lavastones that do something specific for your village. For example, the Totem of Learning will increase your villagers' rate of learning their skills which in turn, of course, makes them more successful as they perform those skills.
Totems can "stack", which means the more you have of that Totem, the power of that Totem increases. Using the example above, if you purchased (stacked) 3 Learning Totems, the rate at which your villagers' learned their skills would be much faster than they were originally.
Most Totems can be stacked 3 times, however, Population Totems can only stack twice. Totems can, however, be lost if you reset your game.