Welcome to TeX.SE! Because you gave no minimal working example with bibliography (MWEB) -- please add an MWE or MWEB in your next question, it helps us to help you! -- I have to guess a little bit.
Please see the following mwe (I added an fictional bib file with package filecontents only to get an compiling mwe, you use your own .bib file):
\RequirePackage{filecontents}
\begin{filecontents*}{\jobname.bib}
@book{Johnson,
author = {Johnson, Jesse C. and Souva, Mark and Smith, Dale L.},
Publisher = {Pearson},
Title = {Physics for Scientists \& Engineers},
Year = {2014},
Date-Added = {2015-10-05 12:23:12 +0000},
Date-Modified = {2015-10-05 12:23:50 +0000},
}
@book{JohnsonE,
author = {Johnson, David C. and Einstein, Albert},
Publisher = {Pearson},
Title = {Physics for Scientists \& Engineers},
Year = {2014},
Date-Added = {2015-10-05 12:23:12 +0000},
Date-Modified = {2015-10-05 12:23:50 +0000},
}
@article{Linzer,
author = {Linzer, Drew A. and Staton, Jeffrey K.},
Title = {Physics for Scientists \& Engineers},
Year = {2014},
}
\end{filecontents*}
\documentclass{article}
\usepackage[%
backend=biber,
style=authoryear,
]{biblatex}
\addbibresource{\jobname.bib}
\begin{document}
Some \cite{Johnson},
%\cite{JohnsonE} % <========================================= uncomment!
and \cite{Linzer}.
%\nocite{*}
\printbibliography
\end{document}
and its result:

Now please uncomment the line
%\cite{JohnsonE} % <========================================= uncomment!
to
\cite{JohnsonE} % <========================================= uncomment!
and compile again three times. Now the result is:

As you can see, now there are two bib entries with the familyname Johnson, but different firstnames. That is the reason why biber adds the initials of the firstnames to create different author names in the bibliography to give you entries you can sure identify ...
As @AlanMunn mentioned in his comment: It's important to note here that biblatex can't distinguish between authors who are in fact the same author if their names in the relevant .bib items are different. So e.g. if you have Johnson, David C. in one and Johnson, David in another they will still get initials. Also that you can turn off this behaviour by using the uniquename option with one of its various values ...
biblatexwill add initials to disambiguate between two authors with the same family name but different given names. If you citeJ. C. JohnsonandA. B. Johnson,biblatexadds the initials to make sure that your readers know that the two Johnsons are different. See https://tex.stackexchange.com/q/134535/35864 – moewe Jun 11 '19 at 17:42style=authoryear, citestyle=authoryear,is equivalent to the shorterstyle=authoryear,– moewe Jun 11 '19 at 17:43uniquenamedo what you want? If so, a short heads-up would be appreciated; if not, you may want to edit your question with more details and explain howuniquenamedoes not work for you. – moewe Jun 13 '19 at 06:10