The paper presents a systematic study of the rest-frame ultraviolet (UV) spectroscopic properties of Lyman Break Galaxies (LBGs) using a database of nearly 1000 LBG spectra. The composite spectra reveal features attributed to hot stars, H II regions, dust, and outflowing neutral and ionized gas. By grouping the database based on galaxy parameters such as Lyα equivalent width, UV spectral slope, and interstellar kinematics, the authors identify major trends in LBG spectra that are less affected by selection effects. They find that LBGs with stronger Lyα emission have bluer UV continua, weaker low-ionization interstellar absorption lines, smaller kinematic offsets between Lyα and interstellar absorption lines, and lower star-formation rates. The study also highlights decoupling between the dependence of low- and high-ionization outflow features on other spectral properties. Additionally, galaxies with rest-frame WLyα ≥ 20 Å in emission exhibit weaker high-ionization lines and stronger nebular emission lines compared to the overall sample. These trends are explained in terms of the properties of large-scale outflows in LBGs, where the appearance of spectra is determined by the covering fraction of outflowing neutral gas containing dust and the range of velocities over which this gas is absorbing. The paper emphasizes the need for higher sensitivity and spectral resolution observations to fully understand the covering fraction and velocity dispersion of outflowing neutral gas in LBGs and its relationship to the escape fraction of Lyman continuum radiation in galaxies at z ~ 3.The paper presents a systematic study of the rest-frame ultraviolet (UV) spectroscopic properties of Lyman Break Galaxies (LBGs) using a database of nearly 1000 LBG spectra. The composite spectra reveal features attributed to hot stars, H II regions, dust, and outflowing neutral and ionized gas. By grouping the database based on galaxy parameters such as Lyα equivalent width, UV spectral slope, and interstellar kinematics, the authors identify major trends in LBG spectra that are less affected by selection effects. They find that LBGs with stronger Lyα emission have bluer UV continua, weaker low-ionization interstellar absorption lines, smaller kinematic offsets between Lyα and interstellar absorption lines, and lower star-formation rates. The study also highlights decoupling between the dependence of low- and high-ionization outflow features on other spectral properties. Additionally, galaxies with rest-frame WLyα ≥ 20 Å in emission exhibit weaker high-ionization lines and stronger nebular emission lines compared to the overall sample. These trends are explained in terms of the properties of large-scale outflows in LBGs, where the appearance of spectra is determined by the covering fraction of outflowing neutral gas containing dust and the range of velocities over which this gas is absorbing. The paper emphasizes the need for higher sensitivity and spectral resolution observations to fully understand the covering fraction and velocity dispersion of outflowing neutral gas in LBGs and its relationship to the escape fraction of Lyman continuum radiation in galaxies at z ~ 3.