Many tutorials and introductions to bash talk about using aliases. Unfortunately, most of them don't cover functions. This is a real loss, because functions offer many values that aliases don't.
Aliases are simple string substitutions. The shell looks at the first word of a command and compares the command against its current list of aliases. Further, if the last character of an alias is a space, it looks at the next word as well. For example:
$ alias 1='echo ' $ alias 2='this is an alias' $ 1 2 this is an alias $
Aliases don't allow for control flow, command-line arguments, or additional trickery that makes the command line so useful. Additionally, the rules surrounding alias expansion are a bit tricky, enough so that the bash(1) man page recommends "To be safe, always put alias definitions on a separate line, and do not use alias[es] in compound commands."