PARSE does not skip leading delimiters, and you cannot specify that you want to parse for white space.
WORD skips leading delimiters, but you cannot specify parsing for white space, it creates a counted string (not the preferred representation), the length of the string is therefore limited (and by the buffer length), it requires a separate buffer (and the copying to that buffer consumes time); WORD also requires passing a delimiter, although skipping leading delimiters only makes sense for white-space delimiters. ANS Forth does not specify the lifetime of the resulting string very much.
PARSE-WORD ( "Skip leading white space and parse name delimited by a white space character.
name " -- c-addr u ) CORE-EXT
c-addr is the address within the input buffer and u is the length of the selected string. If the parse area is empty or contains only white space, the resulting string has a zero length.
PARSE-WORD some-name TYPE
Several systems have implemented a PARSE-WORD compatible with this specification, e.g., Gforth.
A number of systems have been named that define a PARSE-WORD incompatible with this specification (e.g., they often pass a delimiter on the stack). The systems mentioned are MinForth, CHForth, Jforth, 4th. Of these systems MinForth and CHForth are ANS Forth implementations, 4th and JForth are not (although 4th partially stays close to ANS Forth). Coos Haak (CHForth) indicated that the next version of CHForth will have a PARSE-WORD compatible to this specification.