The loose end stitch is very common. You can slip the first stitch without knitting it for a smoother edge, or just make sure that you knit the first and second stitch on the next row tightly so that the loose one from the previous row kind of wraps around the needle and tightens up.
Yarn weight has to do with the thickness of the yarn. Worsted is the most common, but there are some that are very thin that you might use for socks or traditional Fair Isle sweaters, and there are thick, bulky yarns for quick knits.
There are a gazillion patterns out there, and there are a gazillion yarns to go with them. You'll get to know them.