The following plots are fot two groups of simulated normally distributed data, group 1 has mean 10 and group 2 has mean 12.

First plot shows histograms of the two groups:

These data can also be plotted as density plots, where the likely underlying population distribution is being modelled:

A common way to represent this type of data in biology / immunology research is with box-plots (especially if non-normal):

The alterantive is a violin plot. Note it is a density plot tuned on its side and made symetrical:

It’s nice because it ‘shows all the data’ so the reader can decide for themselves the distribution shape. BUT note that violin plots can be manipulated to give different degrees of smoothing, which means the authors’ may have smoothed away any non-normal looking bits of their data. The following plots are the same data as above but with different amounts of smoothing: