  The extended ROentgen Survey with an Imaging Telescope Array (eROSITA) on
board the Spectrum-Roentgen-Gamma (SRG) mission with its first All-Sky Survey
(eRASS1) has offered an unprecedented, comprehensive view of the variable X-ray
sky. With enhanced sensitivity, broader energy coverage, and improved
resolution compared to prior surveys, the eRASS1 Data Release 1 (DR1) catalogue
underwent a variability analysis, focusing on a substantial subset of 128,669
sources. We performed multiple variability tests, utilizing conventional
normalized excess variance, maximum amplitude variability, and Bayesian excess
variance methods. Among the 128,669 DR1 sources, our research identified 557
objects exhibiting variability through NEV and AMPLMAX tests. After applying
suitable thresholds, 108 sources demonstrated significant variability via NEV,
while 73 did so through AMPLMAX. The utilization of the bexvar method extended
our detection capabilities to lower count rates, unveiling a total of 1307
sources manifesting variability. Furthermore, our comparative analysis spanning
2.5 years encompassed observations from consecutive eROSITA surveys, eRASS2,
eRASS3, eRASS4, and eRASS5. Notably, the Gamma-ray burst afterglow GRB 200120A,
which was the most variable DR1 source, was as expected absent in subsequent
eROSITA survey scans. Observations of the Low-Mass X-ray Binary GX 339-4 across
various eROSITA survey scans unveiled substantial variability. These outbursts
involve the movement of the inner radius of the accretion disk, fluctuating
inward and outward. Combining eROSITA and MAXI data reveals that the most
effective tracer for monitoring the onset of the outbursts is the softest
eROSITA band. Magnetically active stars are commonly found among the more
variable X-ray sources. We analyzed the AGN sample to identify variability
patterns and instances of efficiency limit violations.
