It is important to remember that host families have volunteered to host exchange students, and are looking for a good match for their own family. Host families choose you based on your description and on how well you would fit into their family.
A typical Swedish family is usually very busy during the day with work, school or other activities. They usually eat as a whole family once a day, and like to spend their free time together with family. Swedish teenagers are given a lot of freedom, as they are raised to do things independently, with parents really trusting their child and what they are doing on their free time.
Families in Scandinavia generally divide housework among family members equally, so as part of a Swedish family you will have to take on responsibilities such as keeping your room nice and tidy, or helping with dinner, cleaning or the laundry.
Your host family you will treat you as one of their own children, so be prepared for your hosts to ask you about your days at school and what is going on in your life, this is to ensure that you are having a good time. While on exchange it is important to remind yourself that families have accepted you into their home because they are interested in getting to know you and your culture as well as sharing their own culture, so it is important to engage with your hosts and learn from them as they will be happy to answer questions you may have about their life or culture.