[Farox]

Hey, I'm currently studying Japanese in univeristy and have been for the past year, so far with the partical 'Ni' we've mainly been told that it can be used to replace the particle 'he' as in to go to places, e.g:

watashi wa tokyo ni ikimasshita
watashi wa tokyo he ikimashita

these to sentences have exactly the same meaning 'I went to tokyo'

Ni is also used with verbs where you sending and recieving and indicated who or what something is going to i.e:

Ms.Sato gave a book to Mr.Yamada - Satou-san wa Yamada-san ni hon wo agemashita

Mr.Yamada recievied a book from Ms.Sato - Yamada-san wa Sato-san ni hon wo moraimashita

I think with some particles they can be used in many ways that when learning the language you just have to accept them that they are there, we get told that particles act like the 'sign posts' in a sentence, I think with learning the particle you should just learn the verbs which usually go with it, thats how i seem to have done it really. Sorry not really much of a definition there, but hoped it helped a little.