Violin tuning is a huge subject. If you google it you will see.
The violin sounds the very best when you tune the strings into actual perfect fifths that means just fifths not equal fifths. It gives the best resonance all over the instrument. So for that reason violinists have a tendency to tune the instrument with just tuning. But it can give problems.
Sometimes when playing chamber music like string quartet the violin players might tune the E a tad flat, either that or the violin player might avoid using an open E and play the E on the A string instead.
Other times the viola and cello players might tune the C a tad sharp, either that or place a finger at the start of the C string in order to make the open C a tad sharper.
Other times those who play an open string decides the intonation and the others need to adjust to that.
You might ask "Why not tune the instruments with equal temperament?". Well as I said the best resonance happens with just tuning. But violin players might adjust their tuning and intonation according to the music they are playing and with whoom they are playing, like small ensemble, big ensemble or playing with piano.
When tuned with just tuning the flats are often played very flat and the sharps very sharp which can be very expressive. But if you play a C sharp in a sustained A major chord you would actually intonate it slightly flat in order to get a well sounding major chord.
Anyway, some violin players might say that with the equal temperament everything is slightly out of tune. But when you play piano music you will realize that it is actually tolerable, which is why music like Chopin is beautiful.
On violin I think you play with a constant toggling between just and equal temperament.
It is common for beginners to adjust their intonation to the notes on the piano.