Demostratives: This/That

Determiners: This (este, esta, esto) - That (ese, esa, eso o aquel, aquella, aquello)

Use "This" when the object is "near". Here.  (=>)
This is a boy. This is a bike.

Use "That" when the object is "distant/far". There.(=====>)
That is a tree. That is a car.