As in the English 'I love you' and 'I tell you', ti may mean 'to you' or 'you' depending on the verb.
'to you' when the verb is intransitive (ie needs a preposition). Ti parlo = parlo a te.
'you' when the verb is transitive (ie doesn't need a preposition when answering the question 'who/what'). Ex. Ti amo = amo te
I'm not sure about the second part of your comment. What is "this"? Ti is the pronoun for tu which is used when you are talking to/with one person you are in familiar terms with.
If that was a group of people, you'd need to use voi.
If it was a person you are not familiar with or a person you have respect for, then you'd use Lei'.