Q: How is a manuscript ID assigned and what does it mean?

Detailed Question -

What does the Manuscript ID entail? 

2 Answers to this question
Answer:

manuscript id is assigned according to the number of manuscripts received and it useful to communicate 

Answer:

The manuscript ID is a unique number that is assigned by a journal to every submission that it receives. Basically, it is a unique reference point that the journal uses to help the submission system to identify and track the manuscript.

Different journals follow different processes to assign the manuscript ID. Some journals assign it mechanically/automatically as and when they receive the MS, while some of them assign it by article type. The author needs to quote this number each time he/she communicates with the journal as the journal identifies the MS with this number and not by author names. They go back to the manuscript and see the names. All email inquiries, revisions, etc. need this number to be quoted.

Related reading:

What to do if the manuscript ID is not assigned even 1.5 months after submission?