I'm not familiar with the sentence "bed is this trigger" and "bed is this place" that is following next to this sentence. Why does the speaker use "this" rather than "the"?
Answer from a Native speaker
When speaking, many native speakers tend to replace "a" with "this." "This" functions in essentially the same way as "a" and can be used interchangeably. "A" is used in writing ("this" is considered too informal for writing), and "this" might be used when speaking, to replace "a." Generally, using "this" in this way is quite casual and cannot be considered standard English. Ex: There was this [a] huge golden retriever at my friend's house yesterday. Ex: I'm so sorry I'm late! I was stuck behind this [a] guy going only 50 kilometres an hour.