Welcome to a new partner and possibly a new code base.
A team adds and loses members all the time. You worked as a co-op. When you started, you were the “new one.” When you left, the team (hopefully) missed you and your knowledge.
During the first few weeks, someone showed you around, explained the very basics
of the code base, and pointed you to tasks you could do—
During the last few weeks, the team may have asked you to on-board another co-op. It was your turn to explain your code base to a newbie, to answer questions, to point out problems, to fix them. In a short time, you’d be leaving but you acted responsibly. You were socially responsible.
If you never experience any of the above or if you did and disliked how it worked or if you did and liked how it worked, this is your chance to practice, to improve, and/or to forward the advice you got. Point is, practice is the only way to get good at both sides of this critical part of software development.