The objectivity concept, or objectivity principle as it is also known, is the idea that decisions and judgments, usually in accounting, should be made in an unbiased or objective fashion.
It is the theory that decisions should only be based on the direct information to hand, and not take into account other aspects, such as personal opinions.
The objectivity principle is one of the fundamental ethics within the field of accounting, and it helps to ensure information is as factually correct as possible.
This and other standards set within the industry are referred to as GAAP (Generally Accepted Accounting Principles).
Here is a list of some of the considerations which fall under the GAAP:
And here is a short video which explains what GAAP is, and why it's so important:
Essentially, principles like the objectivity principle help to create an element of trust, transparency and also provide predictable standards within the industry of accounting.