Braces in UNIX Shell

Sometimes, you want to immediately follow a variable with a string. This can cause issues if you use the typical grammar of "echo $a" to use a variable, since ksh by default, attempts to do "intelligent" parsing of variable names, but it cannot read your mind.
Compare the difference in output in the following lines:

two=2
print one$twothree
print one${two}three

There is no variable named "twothree", so ksh defaults it to an empty value, for the first print line. However, when you use braces to explicitly show ksh {this is the variable name}, it understands that you want the variable named "two", to be expanded in the middle of those other letters.