What is the difference between a legal separation and a divorce?

My husband and I live in Seattle and own a house together here. We’ve been having problems in our marriage and want to possibly try a legal separation, as we aren’t sure we want a divorce. Is a legal separation possible and what is the difference between a separation and a divorce? How do we file for a legal separation? Also, I want to stay in our house during the separation and my husband is ok with that, but he wants to ensure that he doesn’t lose his interest in the house if he moves out.