It is hard to explain, but imagine that you use это when something is there for you to show it or it isn't, but you can use вот only when you are pointing to something present. So, that and this can in the same way subtitute both это and вот. You need to feel it in the Russian. Give it some time. It is one of the most complicated languages in the world.
Это дерево - моё. (This tree is mine). Дерево is neuter and "это" is used as adjective so changes its form depending on the noun's gender/number. Это моё дерево (This is my tree). Это is subject here so it doesn't change.
Эта кошка - моя.
Это моя кошка.
Эти кошки - мои.
Это мои кошки.