Both are fully mutually intelligible, much like British and Australian English and that spoken in the United States — yet the cultural flavor, pronunciation, and idiomatic expressions give each variety a distinct personality. Continental Portuguese feels concise and compact, whereas Brazilian often feels open and melodic. To understand a bit why, it helps to know that after Portugal started colonizing a huge swath of South America 525 years ago, its language mixed with indigenous tongues such as Tupi-Guarani, languages brought slaves imported from Africa, and later influences from immigrants from Italy, Germany, and elsewhere, sowing the seeds of a more phonetic, flexible variant. It also retained features that are closer to older forms of Portuguese spoken during the colonial period, compared to how the language evolved in Europe. Then after Brazil’s independence in 1822, spelling and usage began to separate further, and although later spelling reforms like those of 1990 (which were put into effect only slowly) have tried to unify spelling, pronunciation, vocabulary, and syntax can still differ quite a bit. To read about some of the main differences, check out my post How Are Continental and Brazilian Portuguese Different?