accent is completely different, but on paper vocab has stark differences, especially since brazil has a lot of influence from the indigenous languages
grammar is different too:
(brazilian) Me manda seu endereço = give me your address
(continental) Manda-me seu endereço = give me your address
doesn't look like much but using "me manda" in portugal is like showing up to a job interview in a t shirt and shorts
the absolute biggest difference is brazil's general lack of a 2nd person
so in portugal you would learn how to conjugate like this:
Ser - to be
Eu sou
Tu és
Ele/Ela é
Nós somos
Vós sois
Eles/Elas são
makes sense right? especially if you've studied french or spanish
but in Brazil you'd learn
Eu sou
Você é
Ele/Ela é
Nós somos
Vocês são
Eles são

notice that there is no "Tu" in brazil and that "você" represents "tu" but is conjugated exactly like the 3rd person of ele/ela, and the same goes for plural ("you all"). so if you were to conjugate exactly to english, for example, you'd say this in portuguese
"Você quer tomar café?"
and this in English:
"Does he want some coffee?" like you're a butler speaking to your employer
back when Portugal colonized Brazil and made everyone speak their language, they made the local tribes and underlings brought over on ships, often from different countries, speak to them like they were masters. they used the word
vossemecê, which meant "your mercy" (like calling a king "your grace" or "your highness"), which became
vosmecê, which today became vocé. nowadays many people just use
cê to mean "you", so at least informally, "cê" has replaced "tu", although the verb is still conjugated in the 3rd person.
to make matters even more confusing, i think in portugal it's really pretentious to use você, AND in some places in brazil, especially but not only Rio, it's popular to use TU, but keep the conjugation of você. and almost the entire country uses the object pronoun of TE, even if they never use TU as the subject pronoun. furthermore, much of the south will actually use TU and the second person conjugation, in addition to a few other places.
this is the most glaring difference, but there are more. remember too that portuguese is spoken in africa, and they speak much more like they do in europe than they do in brazil. but if you go to the Azores or Cape Verde, you'd hardly recognize the language on first listen. CV is actually considered a creole, but Azorean Portuguese is its own dialect, and each of the islands has their own dialect in turn

the first time i heard an azorean blue collar breh speak i questioned whether i actually knew the language or not

its like their version of a thick bayou accent i guess
if you want basic pronunciation differences between brazil and portugal, let me know, because almost everything is wildly different in that regard too, and that's before we discuss the streets, im talking just between newscasters