Using more Gmail features

In the training I have learned there were many features in GMail that I didn't know were there, but will make my time more efficient.  I liked the desktop notifications where I can have important emails show up on my desktop if I'm working on another program.  I have always been confused by the "label" and "archive" structure, but now this makes sense and having multiple labels on a single email will be useful for me.   I have many projects that overlap and the lables feature now makes sense.  I will need to explore the Labs functions more, but I like the calendar and reminders in Gmail.