Learn Portuguese (Portugal): Esse vestido fica-te bem.

In Portuguese, the expression ficar bem is used to say that an item of clothing looks good on someone. Literally, you are saying the dress 'stays well' on you. If it looked bad, you would use the opposite and say fica-te mal.

Why use esse instead of aquele if they both translate to 'that'?

The demonstrative esse is used when the object is physically close to or associated with the person you are talking to. Since you are commenting on a dress the listener is wearing or holding, esse is the correct choice. If the dress were on a mannequin across the room, you would use aquele.

Why is the pronoun -te attached to the end of the verb as fica-te?

In European Portuguese, object pronouns normally attach to the end of the verb with a hyphen in basic affirmative sentences. The pronoun only moves in front of the verb if there is a trigger word, such as a negative word, which would change the order to não te fica bem.

Could I say fica bem a ti instead of fica-te bem?

Yes, you could say fica bem a ti if you wanted to strongly emphasize that it suits YOU, perhaps in contrast to someone else. However, fica-te bem is the standard and most natural way to phrase this in everyday conversation.