A company is a group of people who work towards the same goal, usually in business. It can also refer to a guest or guests in your home.
After they finished college, Seth and David started a small publishing company devoted to poetry. It was tough at first, but now they're doing really well. A few of their books have made it to the best seller list!
I was disappointed that my coffee machine decided to start spraying hot coffee in all directions without warning one day. I was even more disappointed that it happened when we had company over. Mrs. Rittenhouse's blouse was ruined!
Company can also refer to the people someone associates with. In that sense, there are many idioms that use it. You might say someone is in good company, if something that has happened to that person has also happened to someone praiseworthy or notable. Misery loves company expresses the idea that unhappy people like it when others are also unhappy.
One day, I couldn't figure out why my father was so angry with me. Then, I heard him on the phone, arguing with my mother. Misery loves company.