Portuguese in Brazil is from the Portuguese colonization of the Americas, with the first Portuguese immigrants settling in Brazil area in the 16th century. Over time, Portuguese became more prevalent, and by the end of the 18th century, it was the national language. During those years, other colonists from other countries also brought their languages, but by and large, these languages were just absorbed into what would become known as Brazilian Portuguese. 

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So how different are Brazilian Portuguese and European Portuguese? Well, The languages have developed away from each other really since the 16th century; they've also different linguistic influences, which can significantly impact a language. In the case of Brazilian Portuguese, many consider it to have a more nasal sound, while European Portuguese tends to be considered more guttural; also noted are different pronunciations of consonants between the two as well as different vowel lengths, with Brazilian Portuguese vowel being elongated.  That the two differing Portuguese languages would have different vocabulary words, pronouns, verbs, and intonation also makes a lot of sense given the distance between the two areas in which the languages are found. On a personal note, having friends who speak both Brazilian Portuguese and European Portuguese, I have heard there's quite marked difference - with my friends struggling to completely understand the other Portuguese. ​