Connie, you did a great job of putting those donation pieces together. Those are really nice looking blocks, and the brown and black look so good with that blue!
PamelaOry, a leader is a piece of fabric that you feed through your machine in front of the piece you are sewing, so you don't ever have to hold onto your threads or worry about a thread tangle at the beginning of a seam. An ender is the piece you feed through after sewing your last piece, so that your next leader is all set.
As far as I know, it was Bonnie Hunter who came up with the brilliant idea of leader/ender projects. That is, instead of using some scrap piece of fabric as your leader/ender, use actual project units and thus work on two quilts at a time! You can organize and prepare a specific project to use as your leaders/enders, or you can ad lib and just start working on 4-patches or whatever.