Is checking in the same as saving?

If I check in the text boxes once I have done some editing, will that save the file? I'm working on InCopy files from a server. I open them up, check out the text boxes, do some editing and then check them back in. Should I save as well? I don't want to create an extra file, just update the one that's on the server. When I do what I've been doing, I notice that the date and time does not change when I close the file. Have my changes been saved? Thank you all so much!