In general the translation of 'lo que' is 'what' but NOT 'what' as a question
word:
"¿Qué estás haciendo?" "What are you doing?"
'Lo que' is
used to translate the pronoun 'what'. Or 'what' that refers to some idea.
eg.
"Siempre hace lo que tú dices" "He always does what you tell him"
('what' = the thing you tell him)
So whenever we have the meaning "the
thing that" we usually use 'lo que' eg.
"Lo que me gusta más de este
mundo es..." "What I like most about this world is..." (ie. 'the thing I like
most...)
It is important to remember that 'lo que' is neuter, which means
it does not refer to anything which in Spanish is considered masculine or
femenine. In the latter cases, 'el que' or 'la que' must be used. (Plural = 'los
que', 'las que'.)
"¿En qué asiento estabas sentado?" "Pues, el que estaba
al otro lado" "Which seat were you sitting in?" "The one that was at the other
side."
"¿A qué mujer te refieres?" "A la que vimos ayer" "Which woman do
you mean?" "The one we saw yesterday"
Compare:
"Por Carmen es por
LA que se matan los caballeros" "Carmen is the woman gentlemen kill for" (la que
= Carmen)
"Por Carmen es por LO que se matan los caballeros" "Carmen is
what gentlemen kill for" (lo que = the reason (the thing that))