How the speaker knows
How did the speaker find this out?
Meaning
A speaker can show whether information comes from seeing, hearing, being told, or working something out. This separates direct experience from reports and conclusions drawn from clues. Some languages require special forms to mark the source, while others use optional words or phrases. Certainty shows how sure the speaker is; How the speaker knows shows where the information comes from.
How to spot it
Look for words or forms that show the source of the information, rather than just how sure the speaker is.
In your native language
English can state the source with phrases such as I saw, I heard that, or judging by. Apparently can point to a report or a conclusion from clues, so context matters. English does not normally require a verb form that marks the source of each statement.
I heard that the cafe is closing.
The speaker presents the information as something they were told.
Apparently, the shop is closed today.
The speaker relies on a report or clues; the exact source depends on context.
Judging by the wet coats, it's raining outside.
The wet coats are the evidence for the speaker's conclusion.
In your learning language
Spanish does not require a verb ending or other marker to say how the speaker knows something. Speakers can explicitly mention seeing or hearing, or name a reported source with a phrase such as según me ha dicho Ana. Phrases such as por lo que veo can present a conclusion drawn from visible clues, and all these source expressions are optional.
La panadería ya está abierta; lo he visto al pasar.
The bakery is already open; I saw it as I went past.
The speaker explicitly says that they saw this directly.
Según me ha dicho Ana, mañana no hay clase.
According to what Ana told me, there's no class tomorrow.
The phrase identifies another person's report as the source.
Por lo que veo, ya has terminado.
From what I can see, you've already finished.
The speaker presents a conclusion based on what is visible.
Learners whose language marks the information source on every verb may look for a special reported-information form. In Spanish, an ordinary verb form is enough; a source phrase is added when the speaker wants to identify the evidence.