Hey, Deana.
What Sergio says is true, many people will use these particles as if they were the same. But the following should shed some light as to how they are used as grammar dictates.
"La" and "lo" are forms used in accusative, id est when él or ella are the object of the action.
Yo miro a Juán. (I stare at Juán).
Yo lo miro. (I stare at him).
(so, "lo" replaces "él" when receives the action).
Yo veo a Andrea. (I stare at Andrea).
Yo la veo. (I stare at her).
("la" replaces "ella").
Now, if the noun is in the dative position, that is not the object of the action, but the one that receives the consequence of the action, in that case "le" replaces "él" and "ella".
Yo canto una canción para Juán. (I sing a song for Juán)
Yo le canto una canción. (I sing a song for him).
Yo canto una canción para Andrea. (I sing a song for Andrea).
Yo le canto. (I sing for him/her).
("le" replaces the masculine and feminine pronouns in the dative)
In this sentence "una canción" is the accusative:
Yo canto una canción. (I sing a song)
Yo la canto. (I sing it).
Una canción is feminine, therefore can only be replaced by "la" in the accusative pronoun.
Yo canto un verso. (I sing a verse).
Yo lo canto. (I sing it).
Un verso is masculine, so must be replaced by "lo".
Now, if you want to reduce both, accusative and dative to pronouns, "le" will change to "se".
Yo canto una canción para Juán. (I sing a song for Juán).
Yo la canto para Juán. (accusative reduced to "la") (I sing it for Juan)
Yo le canto una canción. (dative reduced to "le") (I sing a song for him)
Yo se la canto. (dative reduced to "se" and accusative reduced to "la") (I sing it for him/her)
Yo le canto un verso a Andrea. (I sing a verso for Andrea)
Yo lo canto a Andrea. (accusative reduced to "lo") (I sing it for Andrea)
Yo le canto un verso. (dative reduced to "le") (I sing a verse for her)
Yo se lo canto. (dative reduced to "se" and accusative reduced to "lo"). (I sing it to him/her)
I hope this helps you.