A parrot does not make an ideal pet for most people it requires much more attention and affection than many other animals do.

Correct sentence - A parrot does not make an ideal pet for most people: it requires much more attention and affection than many other animals do.

When a colon comes before an explanation, a complete sentence typically follows.

This amusement park was created for the employees of the company: the decision was later made to open it to the general public.

Correct sentence - This amusement park was created for the employees of the company; the decision was later made to open it to the general public.

A colon is only correct if the second clause explains the first. Otherwise, a different form of punctuation should be used.

The Giant Tortoise is thought to be the longest-living reptile in the world that is it can survive for up to 300 years.

Correct sentence - The Giant Tortoise is thought to be the longest-living reptile in the world- that is, it can survive for up to 300 years.

A dash can also be used in place of a colon, for the purpose of explaining or clarifying. When this is the case, a sentence that makes sense as a complete thought must be placed before the dash.