1) Translation
ISTO = "this thing" or "these things"
ISSO = "that thing" or "those things"
AQUILO = "that thing" or "those things"
ESTE = "This" (ESTES = "These")
ESSE = "That" (ESSES = "Those")
AQUELE = "That" (AQUELES = "Those")
3)Situations when speak
ISTO is used for a thing or things that are close to the speaker.
ISSO is used for a thing or things that are close to the listener.
AQUILO is used for a thing or things that are distant from both the speaker and the listener.
ESTE is used for a person or a thing that is close to the speaker.
ESSE is used for a person or a thing that is close to the listener.
AQUELE is used for a person or a thing that is distant from both the speaker and the listener.
2) Some considerations when write
ISTO is used for things you're about to write.
ISSO is used for things you've already said or written.
ISTO, ISSO and AQUILO are used when there is no noun (e.g. "Isso é bacana")
ESSE, ESTE and AQUELE usually are used with nouns or adjectives (e.g. "Esta casa")