Colloquially, you always say ve.
But if you want to understand newscasters for example, sometimes “and” is “u” if the noun starts with ב מ פ or a shwa.
Sometimes “and” is “vi” with words starting with a yod. “And children” is “viladim”. That comes up later in this course.
There are more rules, so google “how to say ‘and’ in Hebrew if you’re really interested.
Takeaway point: don’t be surprised to hear either ve or vi or u for “and”.