Two Types of Third Person POV
Third person POV is a popular form of storytelling where the story is told with third person pronouns (he, she, or they) when it comes to the actions and thoughts of the character(s).
There are two different types of third person POV: limited and omniscient. It's important to know the difference between the two and see which one works best for your story.
Third Person Limited: The narrator only knows one character's perspective. As the reader, we only see what is in the one character's mind, and their thoughts on the situation. It's as though the story and plot are filtered, like a veil put over the character's eyes so they can't see the full scenario. For example, plot twists are revealed for both the character(s) and the reader in the same instance. The reader only knows what's going on with the one specific character, and if that one character didn't see the twist coming then neither did the reader. Thus, this is a limited point of view. As long as the POV is focused completely on that one POV character in the moment, then you can also have multiple POVs written in third person limited. Examples of Third Person Limited: Harry Potter, Pride and Prejudice, Game of Thrones, The Giver
Third Person Omniscient: This is where the narrator knows everything. They have knowledge about all the characters and all the situations. There is no veil over the character's eyes, so they can see all of reality. Examples of Third Person Omniscient: The Scarlet Letter, Little Women, Crazy Rich Asians, Good Omens
So, to help kind of wrap it all up, in third person limited the reader can't always be sure that the character(s) is telling the truth or if it's been interpreted to be different. In the third person omniscient, the reader can, because the narrator knows everything. It's up to you how you want your narrator to tell the story to your readers.