We are looking for a report to see what users logged into the system during a certain period of time and also interested if we can see what they did during that time period
I don't believe such a report exists. All you can see is the user's login history from going to User Admin, searching for the user, then clicking on their login (which will be a hyperlink). It will show a history of their logins.
Unfortunately there isn't anything showing what the user did while logged in.