Different morphs are recognized by their color and/or pattern. Spider is (mostly) a pattern morph, meaning it has the usual colors of a normal BP, but the pattern is different. A really easy pattern morph to start to understand it, is the genetic stripe. Although apparently there can be striped snakes that aren't genetic, but it gives you the idea what is meant by pattern.
Cinnamon and Mojave are (mostly) color morphs. The most obvious color morph is the albino. The pattern on a albino BP is exactly the same as on a normal, with the alien heads and all that, but the color is very different.
Some morphs, like albino, are super easy to recognize. Many of them are more subtle, but become easy to recognize by looking at lots of pictures and seeing snakes in person at reptiles shows and such. It just takes time to learn them all.
Het is short for heterozygous. It is a genetic term. You probably know that genes come in pairs. Het means that in a particular pair of genes, there are 2 different ones. For example, one is normal and one is the gene for albino. In talking about BPs, people usually use het to mean a snake is het for one of the recessive traits, and the result is that the snake appears normal, but carries the genetics to produce that recessive trait.
Technically, a mojave (and many other BP morphs) is het. If a snake had 2 mojave genes, it wouldn't appear mojave anymore, it appears leucistic. But usually BP people won't use the term het when talking about co-dom morphs.