Importance of particles

aishiteimasu: love

Watashi-wa anata o aishiteimasu. : I ,you,love: I love you.

"wa"and "o" in the above sentence are called "particles" in terms of Japanese grammar.
In Japanese, particles are more important than the word order in the sentence.

In English, if you make an error in the arrangement of words, the meanings of the sentence may change.
I love you.
You love me.

But in Japanese, if only you put particles in right position, the meaning of the sentence never change.

Watashi-wa anata o aishiteimasu.: I ,you, love: I love you.
Anata o watashi wa aishiteimasu.: You, I, love: I love you.

ageru : give
ni: to

Watashi wa anata ni hon o ageru.: I, you, to, book, give: I give you a book./ I give a book to you.
Watashi wa hon o anata ni ageru.:I, book, you , to ,give: (same )
Hon o watashi wa anata ni ageru.: book, I , you, to ,give:(same)
Anata ni watashi wa hon o ageru.: You, to , I , book, give:(same)