Since I forgot this twice already, I'm writing it here so I can search for it later. And if it helps someone else, that's even better!
char is a single byte (8 bits) representation of a character, in a written language.
wchar_t also represents a character in a written language and can be a single byte or more depending on how the compiler is configured. Microsoft defines wchar_t to be two bytes (16 bits) and to store characters in UTF-16.
WCHAR is a typedef for wchar_t.
TCHAR is a typedef for char or WCHAR depending on the compiler's configuration.
If the compiler is in ANSI or Multi-Byte mode then TCHAR is char.
If the compiler is in Unicode mode then TCHAR is WCHAR.
The LP[x[x]]xxx are typedefs used for defining variables that store addresses to arrays of that type in memory.
LPSTR is (char *) - a pointer to the first char in a string of chars.
LPCSTR is (const char *) - the same as LPSTR, but the string can't be changed.
LPWSTR is (WCHAR *) - a pointer to the first WCHAR in a string of WCHARs.
LPCWSTR is (const WCHAR *) - the same as LPWSTR, but the string can't be changed.
LPTSTR is (TCHAR *) - a pointer to the first char or WCHAR in a string of chars or WCHARs.
LPCTSTR is (const TCHAR *) - the same as LPTSTR, but the string can't be changed.