As addition
"Этот" answers on questions: какой? чей? which one? whose?
"Это" points on thing, object, subject. answers on question: что? what? For example
Что это? What is this?
Посмотри на это! Look at this!
Ты видел это? Did you see this?
Это парк. This is park. We just omit "is". So following is correct:
Это как ты сказал. This is like you said.
Это намного лучше. This is much better.
Это круто. This is cool.
Sometimes usage of "это" is just filling word, to start communication or announce. Like "listen".
Ты, это, не стесняйся, все свои. Hey, listen, don't shy, no strangers here.
Это, пропустите меня! Listen, let me through!
And, for completeness:
Тот парк. That park.
Та книга. That book.
Те парки. Those parks.
То лето. That summer. Previous summer. ( depending on context )
"То". That. Similar to "та", "те", "тот", but being pointing on something, i.e. "that", but implying some certain object/subject, answering on question "what?", not question "which one?" or "whose?".
"Я сделал то, что ты сказал". I did what you said. You did what? Answer: "то, что ты сказал".
"То было раннею весной". That was during early spring. ( very rare usage ) What was? "That" was. То было. In this context, after this sentence should be description what exactly was "that". :)