How do I access the root directory on my Samsung Galaxy J7

[AC Question]

Someone used my cell phone yesterday to supposedly make a call to someone. I realized that he wasn't calling anyone. I took my phone back from him and this came up on my screen:
/system/ app directory/
What does this mean?

 

[ManiacJoe]

Which phone?
Which version of android?
which carrier?

Which app displayed the message?

 

[jasonandrews25788]

it must be rooted I think.