Learn Portuguese (Portugal): O cão chama-se Bobi.

In European Portuguese, pronouns like se usually attach to the end of the verb with a hyphen when the sentence is a basic, positive statement. This rule is called enclisis. Because of this, we write chama-se rather than se chama (which you are more likely to hear if you listen to Brazilian speakers).

What exactly does the -se do in this sentence?

The -se is a reflexive pronoun meaning "himself", "herself", or "itself". The base verb chamar means "to call". Put them together, and chama-se literally translates to "calls itself" or "calls himself". In Portuguese, saying "the dog calls himself..." is the standard way to express "the dog's name is...".

If I wanted to say "My name is Bobi", would I still use chama-se?

No, because the verb and the pronoun always have to match the person you are talking about. Chama-se is strictly for the third person ("he", "she", "it", or the formal "you"). To talk about yourself, you need the "I" form of the verb and the "myself" pronoun: chamo-me.

I always forget how to pronounce the ão in cão. Any tips?

The ão is a nasal diphthong, meaning the sound travels through your nose. To make it, start saying the English sound "ow" (like you just hurt yourself), but pinch off the back of your mouth so the air is forced out through your nose. It sounds a bit like the "oun" in the English word "hound", but you stop before actually pronouncing the 'n'.