In Polish, both ‘i’ and ‘a’ can be translated as ‘and‘… So which should you use?
i is used when you’re connecting similar things together or describing things which are happening at the same time.
Adam i Ewa mieszkają tutaj
Adam and Eve live here
Matka i córka są z Polski
The mother and daughter are from Poland
Jem i piję
I am eating and drinking
a is used when you’re contrasting things or emphasizing that things will happen at different times.
Matka jest z Polski, a córka jest z Włoch
The mother is from Poland and the daughter is from Italy
Jem, a potem będę pić
I am eating and then I will drink
You might also consider ‘a‘ as meaning ‘and/but‘ or ‘whereas‘ if that makes more sense to you.
One small thing worth noting is that ‘a‘ is always preceded by a comma, whereas ‘i‘ is not.