  Spatial, kinematic and orbital properties, along with ages and chemical
compositions of the thin disc, thick disc and various stellar substructures
present in the halo, are studied based on data from the LAMOST and Gaia
surveys. The star formation in the Galactic thin and thick disc, with peak
metallicities of $-0.20$ and $-0.45$ dex, is found to have peaked about 5.5 and
12.5 Gyr ago, respectively. The thin disc is also found to have experienced an
initial star formation burst about 12.5 Gyr ago. The pro-grade population
Splash and hot-disc (HD), with peak metallicity of about $-0.60$ and $-0.43$,
are found to be about 13.03 and 12.21 Gyr old, respectively, with peak
eccentricity of 0.70 and 0.35, are understood to be of in situ origin. The
Gaia-Enceladus/Sausage (GE/S), Thamnos and Sequoia, with peak metallicity of
about $-1.31$, $-1.36$ and $-1.56$, are found to be about 11.66, 12.89 and
12.18 Gyr, respectively, and are understood to be remnants of dwarf galaxies
merged with the Milky Way. The HD, Splash, and Thamnos are found to have
experienced chemical evolution similar to the thick disc while GE/S, Sequoia,
and Helmi stream are found to have experienced distinct chemical enrichment of
iron and $\alpha$-elements.
