I have plotted the density of states (DOS) for my System with Hydrogen-rich and hydrogen lean . When the system is Hydrogen lean, the valence band maximum (HOMO) shifted towards Fermi level and bandgap of the system decreased. How I can explain this DOS in terms of pi, pi*, sigma, sp3, sp2, localization, and delocalization of charge?
As noted by @Camps, you can gain a lot of information from a projected density of states by looking at the contribution of a given orbital. However, it won't directly tell you a lot of information about "bonding character," as you mention in your follow-up comment.
If you are specifically interested in "bonding character" when using a plane-wave DFT code, you're going to need to carry out a population analysis dedicated to such a task. Arguably, your best bet would be to carry out a Crystal Orbital Hamilton Population (COHP) analysis using LOBSTER. Another option that can provide similar orbital-based information is a periodic Natural Bonding Orbital (NBO) analysis, as implemented in this code. There is also the Solid State Adaptive Natural Density Partitioning (SSAdNDP) method, as implemented here.