This is not a tower defense game.

its very simple in a way.. you need health ,energy and to be rested before adventuring.. so you can find or build a rough hut or make it more elaborate.. it will give you a rested bonus and a place to sleep.while you seek out different resources which could make weapons tools food thereby increasing your health and stamina.. but like real life you need to keep eating somewhat regularly or u wont have enuf health to survive a hit or stamina to wield a weapon.. so building a bsae could be part of your plan or you could settle on more humble housing and improve it a little..

Defense is limited to a few items. You can use them creatively to gain a great advantage or use them poorly and have stuff broken all the time.

Technically you don't even need walls if you can just prevent spawns and keep your stuff and yourself hidden.

This is not a PVP game so you don't need to worry too much.

There are no friendly NPCs to hire or use. You do the work. One great plus to this is that you don't need additional resources to repair and everything beyond consumable fuel is returned when deconstructed so you don't need a ton of additional resources to just keep going. Brilliant game design in my opinion. Keeps things simple.

Your goal is progress through the world through the different environments or "biomes". Each one has its own boss to beat.. the resources your gather open up your building/crafting menu and expand as you reach new and more difficult areas.

Many people get stuck on the idea of having one main base but really you don't want to settle on a place too early... start out thinking you are just living out of a small cabin as a temporary home until you progress. Expand as needed and where it benefits you in moving stuff around.

That is how I see the game.

there are many threads on it, but a quick recap for you:
you cannot recruit NPCs really. You can tame some animals, and word is that taming and breeding a great many wolves will defend your base reasonably well. Perhaps a ton of lox as well, but those wreck every rock and tree in sight when angered.
Basically YOU defend the base, and it can't really be attacked when you are not there (or someone is there on multi).

you can construct defenses. The best defenses for an exotic base that you do not want damaged are one or more of these:
- a moat (dig a wide ditch more than a troll club distance away from your construction and at least 2 vikings deep.
- a wall. not a constructed wall, but raised terrain around your base, more or less the inverse of the moat. The enemy must not be able to climb it, you can test with greylings or dwarves easily just wait 2 seconds and one will show up. YOU can climb it if you run at the right spots, and a little practice you can make an 'entry' where you can run up and in without falling or whatnot and without the enemy being able to follow or get inside.

- anti-spawn: put down enough benches and such that nothing can spawn. This is a lot of work, and hiding them can be annoying.
- island: a small island makes the above anti-spawn work much better.

you can also plant spikes that kill weak enemy (and tame animals!) but they are not really very useful for actually stopping serious attacks.

if you want to fight it out and enjoy repairing and rebuilding, you can also try stone walls and rings (so they have to break down a couple of rings before getting to anything important) and similar medieval designs. You can make a high up walkway to shoot from, with 1/2 walls to block incoming fire. Etc. It can be fun, but repairing gets frustrating.

Up until plains, serious protection is not needed. A stake wall and sharp stakes suffice. Even a normal wooden hut will protect you from most enemies but Trolls. You have to lead those away from your base.

Once you hit the plains, things can get serious and you might need a moat around your base. Never had a horde attack so far, which I am surprised about, but you know, it might hit me tonight or tomorrow.

But that's the only attack that needs serious defenses. Trolls wreck everything, except when moats or earth walls are in their way. I don't like them, so I just kite them away and kill them.

the game have pressure ? I mean most of the time i see youtuber fooling around , not show any sign of danger that required a base to defend

Nope, the building aspect is just for the player to rest, craft stuff and respawn.
You can build your base as functional or as expressive as you want.
The game is about exploring a huge world, moving from biome type to biome type and using resources to improve your equipment and stats.
The only defence object is a row of wooden spikes you can put on the ground, you can build walls and towers (piece by piece) or dig a moat if you want.

This encourages you to explore and to set up outposts, but you can make a large lavish hall if you want. (see the Build of the Month pinned topic above for examples)

There are 'events' that can occur randomly if you hang around too long, these events spawn in mobs to attack your base and the types of mobs is based on how far you progressed.
YT'rs mess about a lot because its fun to chill and just work on the base a bit, mix in some hunting, or resource collecting, or explore new biomes etc etc.
It isn't a action game, the combat is decent but not the focus.

Pretty much as Flare said. You COULD get creative and have "defenders" of a sort. For example, you can train wolves to fight for you, or a big furry lizard-ox called "Lox" later on. You can also dig pits and trap larger enemies in there, and have them hold the aggro of some other approaching enemies. (Like having Trolls or Golems guard against Skeletons, blobs, and other monsters that will occasionally try to raid your base).

I get really wrapped up in trying to devise new defenses.