Question: How is the subway system in Chicago?

My daughter and I will visit Chicago in July 24-27. This trip is mainly for my daughter, she will attend a journalist conference there. I only accompany her. We are not going to rent a car, since I am afraid of driving in the city, so I am going to take the advantage of the public transportation in Chicago. The hotel that we are going to stay is close to the location of the conference, but I have to figure out how to spend my time while my daughter goes to the meeting :))

I have had been Chicago once, but that was years ago, and I went with a friend in that time.

Thank you for your advice in advance :)))