  We studied the outburst evolution and timing properties of the recently
discovered X-ray transient MAXI J1348-630 as observed with NICER. We produced
the fundamental diagrams commonly used to trace the spectral evolution, and
power density spectra to study the fast X-ray variability. The main outburst
evolution of MAXI J1348-630 is similar to that commonly observed in black hole
transients. The source evolved from the hard state, through hard- and
soft-intermediate states, into the soft state in the outburst rise, and back to
the hard state in reverse during the outburst decay. At the end of the
outburst, MAXI J1348-630 underwent two reflares with peak fluxes ~1 and ~2
orders of magnitude fainter than the main outburst, respectively. During the
reflares, the source remained in the hard state only, without undergoing any
state transitions, which is similar to the so-called "failed outbursts".
Different types of quasi-periodic oscillations (QPOs) are observed at different
phases of the outburst. Based on our spectral-timing results, we conclude that
MAXI J1348-630 is a black hole candidate.
