A series of words, with each intermeidiate word started with a capital letter. Called "Camel Case" because the capital letters make it look like the humps of a camel.
Hypehated words - like chunks of meat or vegatables on a kebab skewer. Note that cannot case only works in a gew languahes such as Tcl and Perl 6, as the minus sign most usually is the subtraction operator.
Words separated with underscores - the word snakes along past the underscores. Unlike Kebab case which is of limited (language) use, you can use Snake Case with most modern languages.
In Systems Hungarian notation, the prefix encodes the actual data type of the variable.
Apps Hungarian notation strives to encode the logical data type rather than the physical data type; in this way, it gives a hint as to what the variable's purpose is, or what it represents.
Should you use init, initialise or initialize as the name for a piece of setup code? Some languages will force a built in standard on you for such specials, but I strongly recommend that you use your own convention (for your organisation) rather than mixing them up. There's nothing quite so frustrating as typing to debug a piece of code where sometimes the word colour is used, and at other times the word is color.