What is the the use of Ctrl + J in Microsoft Office?

It is used for "Switch a paragraph between justified and left-aligned."

Hi 

This shortcut (ctr-j) to justify paragraph

If the paragraph is Arabic (right to left text direction) it will add some spaces to adjust the lines of paragraph, but if you repress the ctr-j again the alignment will be to the right

If the paragraph is English (left to right text direction) it will add some spaces to adjust the lines of paragraph, but if you repress the ctr-j again the alignment will be to the left

Ctrl+J: Left justify the current paragraph, but keep the right margin justified

Switch a paragraph between justified and left-aligned.

i don't know :(

It justified selected paragraph's alignment from both ends (left and right).

CNTL + J IS USED FOR APPLYING SAME ALIGNMENT FOR PARAGRAPH