When using that instead of where?

Question

The sentence:

We can understand that YouTube has become a channel that / where people visit almost every day.

Can I use "that" instead of "where" here? Why can or can't I? Could you explain that to me?

Answer 1

Both "where" or "that" could be used there, but they have different meanings:

"that" introduces a relative clause that tells you some additional information about the preceding subject/object.

"where" introduces a relative clause that tells you something about the location where something is or happens. (The location can be a physical location, or a metaphorical/conceptual place or context (like a web site, for example))

Therefore,

YouTube has become a channel that people visit almost every day.

This says that people visit YouTube almost every day.

YouTube has become a channel where people visit almost every day.

This says that YouTube is a place, and in that place, people visit (each other) every day.

Note that even many native English speakers get this distinction wrong, however, and people will often use "where" when they mean "that", or vice-versa.

I hope this helps..

(Edit: A bit more context based on additional questions from the comments:)

One thing to note about "that" and its meaning (and when you can use it) is that the use of this word to connect two phrases ("A that B") implies that you can rearrange the phrases so that A is the direct object of B and it will still make sense:

"a channel that people visit" --> "people visit a channel"

If A is actually the subject of B, that's when you should use "which" instead of "that" (but actually, most people don't pay a lot of attention to this distinction anymore, so they often use "that" in that case too, even though it's technically not grammatically correct):

"a channel which (that) is visited by people" --> "a channel is visited by people"

However, if A is not the direct object or subject of B (for example, it's normally joined by another preposition like "in"), then you can't use "that", because if you rearrange things it doesn't actually work:

"a room that we can spend the night" --> "we can spend the night a room" (wrong)

Here, since we spend the night in a room, we would need to use "in which" instead:

"a room in which we can spend the night" --> "we can spend the night in a room" (better!)

The grammatical requirement for "where" is much looser, however. "A where B" does not imply that A serves any specific grammar role within B, it just says that the location associated with A and the location associated with B are the same (or related).

"a channel where people visit" --> "people visit" in the same place as "a channel"
"a room where we can spend the night" --> "we can spend the night" in the same place as "a room"

But this is also why replacing "that" with "where" (or vice-versa) usually changes the meaning, because for most verbs, the direct object ("that") isn't the same thing as the place where it occurs ("where"). (there are a few verbs that do take a location as their direct object, and in those cases you can often interchange them, but only for those verbs)