How do client-server talk securely?

I have covered a story on youtube regarding this. Instead of reading you can even watch it.

Ever wondered

• How we allow users to log in and
• How your Instagram reels are fetched
• Why do Firebase and third parties keep telling us to save tokens
• How frontend and servers talk to each other securely.

Well, this question arrives in my mind way back. When I was new to the servers and clients, I always use to think about how they even talked to each other and who make them talk.

Not a two-way conversation

But we have a culprit right under the nose.
Since our world is full of nonsense and unwanted species so how come software development can be spared from attackers?

It's quite easy to give a connection between client and server it’s just a two-way connection or conversation. I ask you something you reply to me directly.